diff --git a/collects/redex/pict.rkt b/collects/redex/pict.rkt
index 7152103ca3..4d8c67965d 100644
--- a/collects/redex/pict.rkt
+++ b/collects/redex/pict.rkt
@@ -82,7 +82,8 @@
                         'left-right/beside-side-conditions
                         'up-down
                         'up-down/vertical-side-conditions
-                        'up-down/compact-side-conditions))])
+                        'up-down/compact-side-conditions))]
+ [delimit-ellipsis-arguments? (parameter/c any/c)])
 
 (provide/contract
  [label-font-size (parameter/c (and/c (between/c 1 255) integer?))]
diff --git a/collects/redex/private/core-layout.rkt b/collects/redex/private/core-layout.rkt
index c10b4870ee..9052c98859 100644
--- a/collects/redex/private/core-layout.rkt
+++ b/collects/redex/private/core-layout.rkt
@@ -29,6 +29,7 @@
          non-terminal
          literal-style
          metafunction-style
+         delimit-ellipsis-arguments?
          open-white-square-bracket
          close-white-square-bracket
          just-before
@@ -259,7 +260,8 @@
                [(null? (cddr lst))
                 (cons (car lst) (loop (cdr lst)))]
                [else 
-                (if (eq? '... (lw-e (cadr lst)))
+                (if (and (not (delimit-ellipsis-arguments?))
+                         (eq? '... (lw-e (cadr lst))))
                     (cons (car lst)
                           (loop (cdr lst)))
                     (list* (car lst) 
@@ -760,6 +762,7 @@
   (define default-font-size (make-parameter 14))
   (define metafunction-font-size (make-parameter (default-font-size)))
   (define label-font-size (make-parameter 14))
+  (define delimit-ellipsis-arguments? (make-parameter #t))
   
   (define (open-white-square-bracket) (white-bracket "["))
   (define (close-white-square-bracket) (white-bracket "]"))
diff --git a/collects/redex/private/pict.rkt b/collects/redex/private/pict.rkt
index cc997fbf57..1a87a7871e 100644
--- a/collects/redex/private/pict.rkt
+++ b/collects/redex/private/pict.rkt
@@ -36,6 +36,7 @@
          label-style
          literal-style
          metafunction-style
+         delimit-ellipsis-arguments?
          
          label-font-size
          default-font-size
diff --git a/collects/redex/redex.scrbl b/collects/redex/redex.scrbl
index 0050387f20..8d79cf875b 100644
--- a/collects/redex/redex.scrbl
+++ b/collects/redex/redex.scrbl
@@ -2027,6 +2027,13 @@ The @racket['left-right/beside-side-conditions] variant is like
 @racket['left-right], except it puts the side-conditions on the 
 same line, instead of on a new line below the case.}
 
+@defparam[delimit-ellipsis-arguments? delimit? any/c]{
+This parameter controls the typesetting of metafunction definitions
+and applications. When it is non-@racket[#f] (the default), commas
+precede ellipses that represent argument sequences; when it is 
+@racket[#f] no commas appear in those positions.
+}                                                                            
+                                                                            
 @defparam[linebreaks breaks (or/c #f (listof boolean?))]{
   This parameter controls which cases in the metafunction 
   are rendered on two lines and which are rendered on one.
diff --git a/collects/redex/tests/bitmap-test.rkt b/collects/redex/tests/bitmap-test.rkt
index 4b0c5a40d4..de28d2b737 100644
--- a/collects/redex/tests/bitmap-test.rkt
+++ b/collects/redex/tests/bitmap-test.rkt
@@ -197,7 +197,9 @@
    (where (x_3 ...) (rdups x_2 ...))]
   [(rdups) ()])
 
-(test (render-metafunction rdups) "rdups.png")
+(test (render-metafunction rdups) "rdups-delimited.png")
+(parameterize ([delimit-ellipsis-arguments? #f])
+  (test (render-metafunction rdups) "rdups-undelimited.png"))
 
 ;; Non-terminal superscripts
 (test (render-lw lang (to-lw (x_^abcdef x_q^abcdef)))
diff --git a/collects/redex/tests/bmps-macosx/rdups-delimited.png b/collects/redex/tests/bmps-macosx/rdups-delimited.png
new file mode 100644
index 0000000000..a24ee3c1b1
Binary files /dev/null and b/collects/redex/tests/bmps-macosx/rdups-delimited.png differ
diff --git a/collects/redex/tests/bmps-macosx/rdups.png b/collects/redex/tests/bmps-macosx/rdups-undelimited.png
similarity index 100%
rename from collects/redex/tests/bmps-macosx/rdups.png
rename to collects/redex/tests/bmps-macosx/rdups-undelimited.png