Gorlin syndrome is an autosomal dominant disorder characterized by congenital anomalies and tumorigenesis. The gene responsible for Gorlin syndrome is PTCH1, a human homologue of the Drosophila segment polarity gene, patched. We analysed the PTCH1 gene in 25 patients in 22 families with Gorlin syndrome. We detected PTCH1 mutations in 22 patients in 19 families, including insertion/deletion mutations in 13 patients in 11 families (86%), chromosomal deletions in 4 patients in 3 families (16%), nonsense mutations in 2 patients in 2 families (11%), splicing mutations in 3 patients in 3 families (16%), and a missense mutation in 1 patient (5.3%). The sixteen mutations were distributed in extracellular loops (10 mutations: 63%), intracellular loops (four mutations: 25%), and transmembrane portions (two mutations: 13%). Our detection rate of PTCH1 mutations, i.e., 86%, was much higher than those previously reported from other countries. The differences may be derived either from ethnicity or the detection methods.