This report contains the papers presented at the Fourth Workshop on Scheme and Functional Programming. The purpose of the Scheme Workshop is to discuss experience with and future developments of the Scheme programming language—including the future of Scheme standardization—as well as general aspects of computer science loosely centered on the general theme of Scheme. Preface This report contains the papers presented at the Fourth Workshop on Scheme and Functional Programming, which was held on November 7, 2003 in Boston, Massachusetts. Out of twelve papers submitted in response to the call for papers, the program committee chose nine in a virtual meeting. We thank external reviewers Frederic Boussinot, Kent Dybvig, Jonathan Riehl, and Paul Steckler for their generous help. In addition to accepted papers, the committee invited three demonstration talks, which have no entry in these proceedings. (You had to be there.) Paper submission and review were managed using the CONTINUE server—which is implemented in Scheme, of course. We would like to thank Peter Hopkins, of Brown University,