The PLDI conference is one of the premier forums for the presentation of new and exciting research in the areas of programming language design and implementation. The conference attracts a wide audience including researchers, practitioners, and educators. The program committee is pleased to present this proceedings of the 2003 ACM SIGPLAN Conference on Programming Language Design and Implementation which contains a collection of 28 technical papers covering a wide range of exciting topics.This year a total of 131 manuscripts were received from 20 countries. We received 96 submissions from North America, 17 submissions from Europe, 16 submissions from Asia, and 2 submissions from Australia. A total of 36 papers had at least one author from industry. From the 131 submissions, the program committee selected 28 submissions for inclusion in the program.The submission and review process worked as follows. Each submission was assigned to three program committee members for review. In addition, one external review was solicited for each paper. For papers with conflicting reviews email discussions preceded the program committee meeting. For papers with low confidence reviews additional reviews were sought from experts before the program committee meeting. The program committee meeting was held in New Orleans on January 19 and 20. Early in the meeting, the 131 papers were narrowed down to 75 papers whose discussion occupied the rest of the meeting.