This book constitutes the refereed proceedings of the Second International Conference on Principles and Practice of Constraint Programming, CP '96, held in Cambridge, MA, USA in August 1996.<br>The 36 revised full papers presented in the volume were selected from over 100 submissions; also included are abstracts of 22 selected poster presentations and 3 special lectures. CP is the flagship conference series on constraint processing with a number of satellite activities; thus the volume reflects the state of the art in the field.