We have examined alterations in the cyclin-dependent kinase inhibitor 2A (CDKN2A), a major melanoma predisposing gene, in a western-Swedish hereditary melanoma population comprising 107 patients from 68 families. Using sequence analysis and multiplex ligation-dependent probe amplification, we found a novel mutation (Asp108 Tyr), segregating with the disease in three families. This mutation has previously been detected as a somatic mutation in other cancers. We found a previously described Swedish founder mutation (ins113Arg) in one family and a large duplication encompassing the CDKN2A gene locus in another family. Moreover, a debated polymorphism (Ala148Thr) was found in nine families, in which the polymorphism did not segregate with the disease.