Gorlin syndrome (MIM number 109400, gene symbol NBCCS) is a fully penetrant autosomal dominant disorder with over one hundred recognized features. The most frequent and clinically important components are nevoid basal cell carcinomas and odontogenic keratocysts, each affecting about 90 per cent of patients. The non-progressive skeletal anomalies present in a high proportion of cases are helpful diagnostically, as is the presence of ectopic calcification, particularly of the falx, which is present in 90 per cent of cases over the age of 20, and bone cysts. About 70 per cent of individuals have a recognizable appearance, which includes macrocephaly, frontal bossing, hypertelorism and facial milia. Congenital malformations (in 5 per cent of patients) occur at an increased frequency. Ovarian fibromas, medulloblastoma with a peak incidence at 2 years of age and cardiac fibromas are also important components of the syndrome.