The papers contained in this volume were presented at the 12th Annual S- posium on Combinatorial Pattern Matching, held July 1{4, 2001 at the Dan Panorama Hotel in Jerusalem, Israel. They were selected from 35 abstracts s- mitted inresponse to the call for papers. In addition,there were invited lectures by Aviezri Fraenkel (Weizmann Institute of Science), Zvi Galil (Columbia), Rao Kosaraju (Johns Hopkins University), and Uzi Vishkin(Technion and U. Ma- land). This year the call for papers invited short (poster) presentations. They also appear in the proceedings. Combinatorial Pattern Matching (CPM) addresses issues of searching and matching strings and more complicated patterns such as trees, regular expr- sions,graphs,pointsets, andarrays,invariousformats.Thegoalistoderiven- trivialcombinatorialproperties ofsuchstructures andtoexploitthese properties in order to achieve superior performance for the corresponding computational problems. On the other hand, an important aim is to analyze and pinpoint the properties and conditions under which searches can not be performed e ciently. Overthepastdecadeasteady ?owofhighqualityresearch onthissubject has changed a sparse set of isolated results into a full-?
edged area of algorithmics. This area is continuing to grow even further due to the increasing demand for speed and e ciency that stems from important applications such as the World Wide Web, computational biology, computer vision, and multimedia systems. These involverequirements forinformationretrieval inheterogeneous databases, data compression, and pattern recognition. The objective of the annual CPM gathering is to provide an international forum for the presentation of research results in combinatorial pattern matching and related applications.