This book constitutes the refereed proceedings of the 34th International Symposium on Logic-Based Program Synthesis and Transformation, LOPSTR 2024, held in Milan, Italy, during September 9-10, 2024. The 12 full papers and 1 short paper included in this book were carefully reviewed and selected from 28 submissions. They were organized in topical sections as follows: Synthesis and Transformation; Decision Procedures; Deployment; Specification, Refactoring and Testing; and Term and Graph Rewriting.