The papers contained in this volume were presented at the Fourth Annual Symposium on Combinatorial Pattern Matching, held in Padova, Italy, in June 1993. Combinatorial pattern matching addresses issues of searching and matching of strings and more complicated patterns such as trees, regular expressions, extended expressions, etc. The goal is to derive nontrivial combinatorial properties for such structures and then to exploit these properties in order to achieve superior performance for the corresponding computational problems. In recent years, a steady flow of high-quality scientific studies of this subject has changed a sparse set of isolated results into a full-fledged area of algorithmics. The area is expected to grow even further due to the increasing demand for speedand efficiency that comes especially from molecular biology and the Genome project, but also from other diverse areas such as information retrieval, pattern recognition, compilers, data compression, and program analysis.