diff --git a/collects/profile/analyzer.rkt b/collects/profile/analyzer.rkt
index 664aee7..e114c4e 100644
--- a/collects/profile/analyzer.rkt
+++ b/collects/profile/analyzer.rkt
@@ -4,7 +4,7 @@
 
 (provide analyze-samples)
 
-(require "structs.ss" "utils.ss" scheme/list)
+(require "structs.rkt" "utils.rkt" scheme/list)
 
 (define-syntax-rule (with-hash <hash> <key> <expr>)
   (hash-ref! <hash> <key> (lambda () <expr>)))
diff --git a/collects/profile/main.rkt b/collects/profile/main.rkt
index 3c29bf0..af10381 100644
--- a/collects/profile/main.rkt
+++ b/collects/profile/main.rkt
@@ -2,8 +2,8 @@
 
 (provide profile-thunk profile)
 
-(require "sampler.ss" "analyzer.ss"
-         (prefix-in text: "render-text.ss")
+(require "sampler.rkt" "analyzer.rkt"
+         (prefix-in text: "render-text.rkt")
          (for-syntax scheme/base))
 
 (define (profile-thunk thunk
@@ -74,7 +74,7 @@
   (thread bg-fib)
   (list (fibs n) (channel-get ch)))
 
-(require "render-graphviz.ss")
+(require "render-graphviz.rkt")
 
 (profile ;(fibs 40)
          ;(dynamic-require '(lib "scribblings/reference/reference.scrbl") #f)
diff --git a/collects/profile/render-graphviz.rkt b/collects/profile/render-graphviz.rkt
index 946a15f..1aba7ce 100644
--- a/collects/profile/render-graphviz.rkt
+++ b/collects/profile/render-graphviz.rkt
@@ -2,7 +2,7 @@
 
 (provide render)
 
-(require "structs.ss" "analyzer.ss" "utils.ss")
+(require "structs.rkt" "analyzer.rkt" "utils.rkt")
 
 (define (render profile
                 #:hide-self [hide-self% 1/100]
diff --git a/collects/profile/render-text.rkt b/collects/profile/render-text.rkt
index 8cda73a..a0952fc 100644
--- a/collects/profile/render-text.rkt
+++ b/collects/profile/render-text.rkt
@@ -2,7 +2,7 @@
 
 (provide render)
 
-(require "structs.ss" "analyzer.ss" "utils.ss" scheme/list)
+(require "structs.rkt" "analyzer.rkt" "utils.rkt" scheme/list)
 
 (define (f:msec msec)
   (number->string (round (inexact->exact msec))))
diff --git a/collects/profile/utils.rkt b/collects/profile/utils.rkt
index f355340..7486ce3 100644
--- a/collects/profile/utils.rkt
+++ b/collects/profile/utils.rkt
@@ -1,6 +1,6 @@
 #lang scheme/base
 
-(require "structs.ss" scheme/list scheme/nest)
+(require "structs.rkt" scheme/list scheme/nest)
 
 ;; Format a percent number, possibly doing the division too.  If we do the
 ;; division, then be careful: if we're dividing by zero, then make the result
diff --git a/collects/tests/profile/main.rkt b/collects/tests/profile/main.rkt
index fd6a2e3..27f9397 100644
--- a/collects/tests/profile/main.rkt
+++ b/collects/tests/profile/main.rkt
@@ -1,7 +1,7 @@
 #lang scheme/base
 
 (require tests/eli-tester profile/structs profile/analyzer
-         scheme/match scheme/list "topsort.ss")
+         scheme/match scheme/list "topsort.rkt")
 
 (define A '(A . #f))
 (define B '(B . #f))
diff --git a/collects/tests/profile/topsort.rkt b/collects/tests/profile/topsort.rkt
index edadb61..e4f3f79 100644
--- a/collects/tests/profile/topsort.rkt
+++ b/collects/tests/profile/topsort.rkt
@@ -96,7 +96,7 @@
                 '((A) (B)))
 
    ;; this is an example using the actual times for the A->B->A case that is
-   ;; tested in main.ss
+   ;; tested in main.rkt
    (same-levels '(* 2->1 A 1->2 B 2->1 A 1->2 *)
                 '((A) (B)))