This book constitutes the refereed proceedings of the 5th Asian Symposium on Programming Languages and Systems, APLAS 2007, held in Singapore, in November/December 2007.

The 25 revised full papers presented together with 3 invited talks were carefully reviewed and selected from 84 submissions. The symposium addresses all issues in programming languages and systems - ranging from foundational to practical issues. The papers focus on topics such as semantics, logics, foundational theory, type systems, language design, program analysis, optimization, transformation, software security, safety, verification, compiler systems, interpreters, abstract machines, domain-specific languages and systems, as well as programming tools and environments.