Description:This book constitutes the refereed proceedings of the 21st International Conference on Logic and Programming, ICLP 2005, held in Barcelona, Spain, in October 2005.The 25 revised full papers and 15 revised poster papers presented together with 4 invited papers and 7 abstracts of a poster session of a doctoral consortium were carefully reviewed and selected from 104 submissions. The papers cover all issues of current research in logic programming. Extra attention is given to novel applications of logic programming and work providing novel integrations of different areas.