diff --git a/chapter2.lisp b/chapter2.lisp
index aa1c86c..d9a6980 100644
--- a/chapter2.lisp
+++ b/chapter2.lisp
@@ -118,3 +118,8 @@ and upper bound."
   (make-interval (* c (- 1 (/ p 100)))
 		 (* c (+ 1 (/ p 100)))))
 
+;; Exercise 2.17
+(defun last-pair (l)
+  (if (null (cdr l))
+      l
+      (last-pair (cdr l))))