It is our great pleasure to introduce the proceedings of the 20th anniversary edition of the Annual Symposium on Combinatorial Pattern Matching (CPM). The meeting was held in Lille, France,hosted by the Laboratoired'Informatique Fondamentale de Lille (LIFL) a?liated with the Universit' e de Lille 1 and the French Centre National de Recherche Scienti?que (CNRS), as well as by INRIA Lille - Nord Europe. Started in 1990as a summer school with about 30 invited participants, CPM quicklyevolvedintoarepresentativeannualinternationalconference.Principally motivated by combinatorial algorithms for search problems in strings (texts, sequences), the scope of CPM extended to more complex data structures such astrees,graphs,two-dimensionalarrays,or setsof points.Thosestudiesresulted inarichcollectionofalgorithmictechniquesanddatastructures,makingbridges to other parts of the theory of discrete algorithms and algorithm engineering. Today, the area of combinatorial pattern matching is a well-identi?ed active sub?eld of algorithmic research. Importantly, this development has been fertilized by a number of major - plication areas providing direct motivations and fruitful feedback to the CPM problematics. Those applications include data compression, computational bi- ogy,Internetsearch,datamining,informationretrieval,coding,naturallanguage processing,pattern recognition,music analysis, and others. On the one hand, all these areas make use of combinatorial pattern matching techniques and, on the otherhand,raisenewpatternmatchingproblems.Forexample,the fastprogress in computational molecular biology, triggered in the 1990s by the availability of mass genomic data, considerably in?uenced the combinatorial pattern matching ?eld: as an illustration, about one-third of the papers presented in this volume deal with problems related to bioinformatics applications.