diff --git a/README.md b/README.md
index 6f198ddf..3d863f39 100644
--- a/README.md
+++ b/README.md
@@ -4,18 +4,18 @@
 
 ### One-time Method
 
-From a terminal, execute your lisp interpreter on the file 'contemplate.lsp' e.g.
+From a terminal, execute your lisp interpreter on the file 'contemplate.lisp' e.g.
 
-    abcl --noinform --noinit --load contemplate.lsp --eval '(quit)'
-    ccl -n -l contemplate.lsp -e '(quit)'
-    clisp -q -norc -ansi contemplate.lsp
-    ecl -norc -load contemplate.lsp -eval '(quit)'
-    sbcl --script contemplate.lsp
+    abcl --noinform --noinit --load contemplate.lisp --eval '(quit)'
+    ccl -n -l contemplate.lisp -e '(quit)'
+    clisp -q -norc -ansi contemplate.lisp
+    ecl -norc -load contemplate.lisp -eval '(quit)'
+    sbcl --script contemplate.lisp
 
 ### Watching the Koans
 
 On Linux and MacOS systems, the shell scripts `meditate-linux.sh` and
-`meditate-macos.sh` can be used to automatically evaluate 'contemplate.lsp'
+`meditate-macos.sh` can be used to automatically evaluate 'contemplate.lisp'
 whenever the koan files are modified, providing immediate feedback on changes
 to the koans. To run the MacOS version you need to have
 [`fswatch`](https://github.com/emcrisostomo/fswatch) installed. From a terminal:
@@ -36,7 +36,7 @@ You have not yet reached enlightenment ...
   A koan is incomplete.
 
 Please meditate on the following code:
-   File "koans/asserts.lsp"
+   File "koans/asserts.lisp"
    Koan "ASSERT-TRUE"
    Current koan assert status is "(INCOMPLETE)"
 
@@ -44,7 +44,7 @@ You are now 0/169 koans and 0/25 lessons closer to reaching enlightenment
 ```
 
 This indicates that the script has completed, and that the learner should look
-to asserts.lsp to locate and fix the problem.  The problem will be within
+to asserts.lisp to locate and fix the problem.  The problem will be within
 a define-test expression such as
 
     (define-test assert-true
@@ -81,5 +81,5 @@ For information and instructions on installing Quicklisp
 please see:
 https://www.quicklisp.org/beta/
 The user can either remove #+quicklisp and uncomment
-(load "~/.quicklisp/setup.lisp") in threads.lsp, or  if they know
-quicklisp will be loaded while running contemplate.lsp do nothing.
+(load "~/.quicklisp/setup.lisp") in threads.lisp, or  if they know
+quicklisp will be loaded while running contemplate.lisp do nothing.
diff --git a/contemplate.lsp b/contemplate.lisp
similarity index 88%
rename from contemplate.lsp
rename to contemplate.lisp
index d252dfd9..eb892bf5 100644
--- a/contemplate.lsp
+++ b/contemplate.lisp
@@ -15,13 +15,13 @@
 (in-package :cl-user)
 
 ;;; Though Clozure / CCL runs lisp-koans on the command line using
-;;; "ccl -l contemplate.lsp", the following lines are needed to
+;;; "ccl -l contemplate.lisp", the following lines are needed to
 ;;; meditate on the koans within the CCL IDE.
 ;;; (The :hemlock is used to distiguish between ccl commandline and the IDE)
 #+(and :ccl :hemlock)
 (setf *default-pathname-defaults* (directory-namestring *load-pathname*))
 
-(load "test-framework.lsp")
-(load "lisp-koans.lsp")
+(load "test-framework.lisp")
+(load "lisp-koans.lisp")
 
 (com.google.lisp-koans:main)
diff --git a/koans/arrays.lsp b/koans/arrays.lisp
similarity index 100%
rename from koans/arrays.lsp
rename to koans/arrays.lisp
diff --git a/koans/asserts.lsp b/koans/asserts.lisp
similarity index 100%
rename from koans/asserts.lsp
rename to koans/asserts.lisp
diff --git a/koans/atoms-vs-lists.lsp b/koans/atoms-vs-lists.lisp
similarity index 100%
rename from koans/atoms-vs-lists.lsp
rename to koans/atoms-vs-lists.lisp
diff --git a/koans/clos.lsp b/koans/clos.lisp
similarity index 100%
rename from koans/clos.lsp
rename to koans/clos.lisp
diff --git a/koans/condition-handlers.lsp b/koans/condition-handlers.lisp
similarity index 100%
rename from koans/condition-handlers.lsp
rename to koans/condition-handlers.lisp
diff --git a/koans/control-statements.lsp b/koans/control-statements.lisp
similarity index 100%
rename from koans/control-statements.lsp
rename to koans/control-statements.lisp
diff --git a/koans/dice-project.lsp b/koans/dice-project.lisp
similarity index 100%
rename from koans/dice-project.lsp
rename to koans/dice-project.lisp
diff --git a/koans/equality-distinctions.lsp b/koans/equality-distinctions.lisp
similarity index 100%
rename from koans/equality-distinctions.lsp
rename to koans/equality-distinctions.lisp
diff --git a/koans/evaluation.lsp b/koans/evaluation.lisp
similarity index 100%
rename from koans/evaluation.lsp
rename to koans/evaluation.lisp
diff --git a/koans/extra-credit.lsp b/koans/extra-credit.lisp
similarity index 100%
rename from koans/extra-credit.lsp
rename to koans/extra-credit.lisp
diff --git a/koans/format.lsp b/koans/format.lisp
similarity index 100%
rename from koans/format.lsp
rename to koans/format.lisp
diff --git a/koans/functions.lsp b/koans/functions.lisp
similarity index 100%
rename from koans/functions.lsp
rename to koans/functions.lisp
diff --git a/koans/hash-tables.lsp b/koans/hash-tables.lisp
similarity index 100%
rename from koans/hash-tables.lsp
rename to koans/hash-tables.lisp
diff --git a/koans/iteration.lsp b/koans/iteration.lisp
similarity index 100%
rename from koans/iteration.lsp
rename to koans/iteration.lisp
diff --git a/koans/lists.lsp b/koans/lists.lisp
similarity index 100%
rename from koans/lists.lsp
rename to koans/lists.lisp
diff --git a/koans/loops.lsp b/koans/loops.lisp
similarity index 100%
rename from koans/loops.lsp
rename to koans/loops.lisp
diff --git a/koans/macros.lsp b/koans/macros.lisp
similarity index 100%
rename from koans/macros.lsp
rename to koans/macros.lisp
diff --git a/koans/mapcar-and-reduce.lsp b/koans/mapcar-and-reduce.lisp
similarity index 100%
rename from koans/mapcar-and-reduce.lsp
rename to koans/mapcar-and-reduce.lisp
diff --git a/koans/multiple-values.lsp b/koans/multiple-values.lisp
similarity index 100%
rename from koans/multiple-values.lsp
rename to koans/multiple-values.lisp
diff --git a/koans/nil-false-empty.lsp b/koans/nil-false-empty.lisp
similarity index 100%
rename from koans/nil-false-empty.lsp
rename to koans/nil-false-empty.lisp
diff --git a/koans/scope-and-extent.lsp b/koans/scope-and-extent.lisp
similarity index 100%
rename from koans/scope-and-extent.lsp
rename to koans/scope-and-extent.lisp
diff --git a/koans/scoring-project.lsp b/koans/scoring-project.lisp
similarity index 100%
rename from koans/scoring-project.lsp
rename to koans/scoring-project.lisp
diff --git a/koans/special-forms.lsp b/koans/special-forms.lisp
similarity index 100%
rename from koans/special-forms.lsp
rename to koans/special-forms.lisp
diff --git a/koans/std-method-comb.lsp b/koans/std-method-comb.lisp
similarity index 100%
rename from koans/std-method-comb.lsp
rename to koans/std-method-comb.lisp
diff --git a/koans/strings.lsp b/koans/strings.lisp
similarity index 100%
rename from koans/strings.lsp
rename to koans/strings.lisp
diff --git a/koans/structures.lsp b/koans/structures.lisp
similarity index 100%
rename from koans/structures.lsp
rename to koans/structures.lisp
diff --git a/koans/threads.lsp b/koans/threads.lisp
similarity index 100%
rename from koans/threads.lsp
rename to koans/threads.lisp
diff --git a/koans/triangle-project.lsp b/koans/triangle-project.lisp
similarity index 100%
rename from koans/triangle-project.lsp
rename to koans/triangle-project.lisp
diff --git a/koans/type-checking.lsp b/koans/type-checking.lisp
similarity index 100%
rename from koans/type-checking.lsp
rename to koans/type-checking.lisp
diff --git a/koans/variables-parameters-constants.lsp b/koans/variables-parameters-constants.lisp
similarity index 100%
rename from koans/variables-parameters-constants.lsp
rename to koans/variables-parameters-constants.lisp
diff --git a/koans/vectors.lsp b/koans/vectors.lisp
similarity index 100%
rename from koans/vectors.lsp
rename to koans/vectors.lisp
diff --git a/lisp-koans.lsp b/lisp-koans.lisp
similarity index 96%
rename from lisp-koans.lsp
rename to lisp-koans.lisp
index 0e25585a..d754cea4 100644
--- a/lisp-koans.lsp
+++ b/lisp-koans.lisp
@@ -32,7 +32,7 @@
 
 (defun load-koan-group-named (koan-group-name)
   (let* ((koan-name (string-downcase (string koan-group-name)))
-         (koan-file-name (concatenate 'string koan-name ".lsp"))
+         (koan-file-name (concatenate 'string koan-name ".lisp"))
          (koan-package-name (package-name-from-group-name koan-group-name)))
     (unless (find-package koan-package-name)
       (make-package koan-package-name
@@ -96,7 +96,7 @@
     (format t "You have not yet reached enlightenment.
     ~A
 Please meditate on the following code:
-    File \"koans/~(~A~).lsp\"
+    File \"koans/~(~A~).lisp\"
     Koan \"~A\"
     Current koan assert status is \"~A\"~%~%"
             (koan-status-message koan-status) filename koan-name koan-status)))
@@ -106,7 +106,7 @@
 That was the last one, well done! ENLIGHTENMENT IS YOURS!
 *********************************************************
 
-If you demand greater challenge, take a look at extra-credit.lsp
+If you demand greater challenge, take a look at extra-credit.lisp
 Or, let the student become the teacher:
 Write and submit your own improvements to https://github.com/google/lisp-koans!
 "))
diff --git a/meditate-linux.sh b/meditate-linux.sh
index 048dda85..1a811327 100644
--- a/meditate-linux.sh
+++ b/meditate-linux.sh
@@ -9,19 +9,19 @@ fi
 choose_command_line() {
     case "$1" in
         'abcl' )
-            echo "abcl --noinform --noinit --load contemplate.lsp --eval '(quit)'"
+            echo "abcl --noinform --noinit --load contemplate.lisp --eval '(quit)'"
         ;;
         'ccl' )
-            echo "ccl -n -l contemplate.lsp -e '(quit)'"
+            echo "ccl -n -l contemplate.lisp -e '(quit)'"
         ;;
         'clisp' )
-            echo "clisp -q -norc -ansi contemplate.lsp"
+            echo "clisp -q -norc -ansi contemplate.lisp"
         ;;
         'ecl' )
-            echo "ecl -norc -load contemplate.lsp -eval '(quit)'"
+            echo "ecl -norc -load contemplate.lisp -eval '(quit)'"
         ;;
         'sbcl' )
-            echo "sbcl --script contemplate.lsp"
+            echo "sbcl --script contemplate.lisp"
         ;;
         * )
             echo ""
diff --git a/meditate-macos.sh b/meditate-macos.sh
index 8ac0116c..ca184013 100644
--- a/meditate-macos.sh
+++ b/meditate-macos.sh
@@ -9,19 +9,19 @@ fi
 choose_command_line() {
     case "$1" in
         'abcl' )
-            echo "abcl --noinform --noinit --load contemplate.lsp --eval '(quit)'"
+            echo "abcl --noinform --noinit --load contemplate.lisp --eval '(quit)'"
         ;;
         'ccl' )
-            echo "ccl -n -l contemplate.lsp -e '(quit)'"
+            echo "ccl -n -l contemplate.lisp -e '(quit)'"
         ;;
         'clisp' )
-            echo "clisp -q -norc -ansi contemplate.lsp"
+            echo "clisp -q -norc -ansi contemplate.lisp"
         ;;
         'ecl' )
-            echo "ecl -norc -load contemplate.lsp -eval '(quit)'"
+            echo "ecl -norc -load contemplate.lisp -eval '(quit)'"
         ;;
         'sbcl' )
-            echo "sbcl --script contemplate.lsp"
+            echo "sbcl --script contemplate.lisp"
         ;;
         * )
             echo ""
diff --git a/test-framework.lsp b/test-framework.lisp
similarity index 100%
rename from test-framework.lsp
rename to test-framework.lisp
diff --git a/unused-test-ideas.lsp b/unused-test-ideas.lisp
similarity index 100%
rename from unused-test-ideas.lsp
rename to unused-test-ideas.lisp