MatInspector is a software tool that utilizes a large library of matrix descriptions for transcription factor binding sites to locate matches in DNA sequences. MatInspector is almost as fast as a search for IUPAC strings but has been shown to produce superior results. It assigns a quality rating to matches and thus allows quality-based filtering and selection of matches. The first version of MatInspector is described in Quandt et al., 1995 (NAR). A paper describing various new features of MatInspector has been published in 2005 (Cartharius et al., 2005, Bioinformatics).