Somatic FGFR3 mutations have recently been identified in seborrheic keratoses (SK). Affected individuals often show a large number of SK, but their spectrum of FGFR3 mutations has not been investigated yet. We analyzed 78 SK of four patients using a SNaPshot multiplex assay. FGFR3 mutations were detected in 46 of 78 SK (59%). The mutation rates of the patients ranged from 26 to 89%. Each patient showed at least four different mutated loci. FGFR3 mutations appear to be common genetic alterations in multiple SK with a varying interindividual mutation frequency but without specific intraindividual hot spots.