This book constitutes the thoroughly refereed and extended post-workshop proceedings of the 12th Annual ERCIM International Workshop on Constraint Solving and Constraint Logic Programming, CSCLP 2007, held in Rocquencourt, France, in June 2007. The 10 revised full papers presented were carefully reviewed and selected from 16 initial submissions. The papers address all aspects of constraint and logic programming, including foundational issues, implementation techniques, new applications as well as teaching issues. Particular emphasis is placed on assessing the current state of the art and identifying future directions.