This book constitutes the refereed proceedings of the First International Conference on Computational Logic, CL 2000, held in London, UK in July 2000. The 86 revised full papers presented together with five invited papers were carefully reviewed and selected from a total of 176 submissions. In accordance with the seven streams, the papers are organized in sections on program development, logic programming - theory and extensions, constraints, automated deduction - putting theory into practice, knowledge representation and nonmonotonic reasoning, database systems, and logic programming - implementations and applications.