This paper presents iNFAnt, a parallel engine for regular expression pattern matching. In contrast with traditional approaches, iNFAnt adopts non-deterministic automata, allowing the compilation of very large and complex rule sets that are otherwise hard to treat. iNFAnt is explicitly designed and developed to run on graphical processing units that provide large amounts of concurrent threads; this parallelism is exploited to handle the non-determinism of the model and to process multiple packets at once, thus achieving high performance levels. Categories and Subject Descriptors C.2.3 [Computer-Communication Networks]: Network Operations General Terms Experimentation, Algorithms Keywords NFA, pattern matching, CUDA, GPGPU, regular expression