diff --git a/R6RS-TODO.txt b/R6RS-TODO.txt
index c47fd9f..3b79421 100644
--- a/R6RS-TODO.txt
+++ b/R6RS-TODO.txt
@@ -18,7 +18,6 @@ TODO for (R6RS BASE)
   - Make sure the following primitives work:
     
     rationalize
-    numerator           denominator
 
     make-rectangular    make-polar 
     real-part           imag-part
@@ -87,3 +86,4 @@ TODO for (R6RS BASE)
 
 
 Completed for (R6RS BASE):
+    numerator           denominator
diff --git a/src/ikarus.boot b/src/ikarus.boot
index e4a2bf5..c64bf48 100644
Binary files a/src/ikarus.boot and b/src/ikarus.boot differ
diff --git a/src/ikarus.numerics.ss b/src/ikarus.numerics.ss
index 7d81a1e..665c1d2 100644
--- a/src/ikarus.numerics.ss
+++ b/src/ikarus.numerics.ss
@@ -28,7 +28,7 @@
 
 (library (ikarus generic-arithmetic)
   (export + - * / zero? = < <= > >= add1 sub1 quotient remainder
-          positive? expt gcd lcm
+          positive? expt gcd lcm numerator denominator
           quotient+remainder number->string string->number)
   (import 
     (ikarus system $fx)
@@ -38,7 +38,7 @@
     (ikarus system $strings)
     (except (ikarus) + - * / zero? = < <= > >= add1 sub1 quotient
             remainder quotient+remainder number->string positive?
-            string->number expt gcd lcm))
+            string->number expt gcd lcm numerator denominator))
 
   (define (fixnum->flonum x)
     (foreign-call "ikrt_fixnum_to_flonum" x))
@@ -1023,7 +1023,19 @@
         [(fixnum? x) (foreign-call "ikrt_fx_sqrt" x)]
         [else (error 'sqrt "unsupported ~s" x)])))
 
+  (define numerator
+    (lambda (x)
+      (cond
+        [(ratnum? x) ($ratnum-n x)]
+        [(or (fixnum? x) (bignum? x)) x]
+        [else (error 'numerator "~s is not an exact integer" x)])))
 
+  (define denominator
+    (lambda (x)
+      (cond
+        [(ratnum? x) ($ratnum-d x)]
+        [(or (fixnum? x) (bignum? x)) 1]
+        [else (error 'denominator "~s is not an exact integer" x)])))
 
   (define string->number
     (lambda (x)
diff --git a/src/makefile.ss b/src/makefile.ss
index 42aba4b..05b4554 100755
--- a/src/makefile.ss
+++ b/src/makefile.ss
@@ -381,6 +381,8 @@
     [flonum->string          i]
     [gcd                     i r]
     [lcm                     i r]
+    [numerator               i r]
+    [denominator             i r]
     [symbol?                 i r symbols]
     [gensym?                 i symbols]
     [gensym                  i symbols]