This book constitutes the refereed proceedings of the 12th Annual Symposium on Combinatorial Pattern Matching, CPM 2001, held in Jerusalem, Israel, in July 2001.The 21 revised papers presented together with one invited paper were carefully reviewed and selected from 35 submissions. The papers are devoted to current theoretical and algorithmic issues of searching and matching strings and more complicated patterns such as trees, regular expressions, graphs, point sets, and arrays as well as to advanced applications of CPM in areas such as the Internet, computational biology, multimedia systems, information retrieval, data compression, coding, computer vision, and pattern recognition.