This book constitutes the refereed proceedings of the International Workshop on Principles and Practice of Semantic Web Reasoning, PPSWR 2003, held in Mumbai, India in December 2003 as satellite meeting of ICLP 2003. The 13 revised full papers presented were carefully reviewed and selected for inclusion in the proceedings. The papers are organized in topical sections on foundations of semantic Web reasoning, reasoning in practice, query- and rule-languages, and semantics and knowledge representation.