Our data suggest that in most clinical settings, testing for CDKN2A mutations is very unlikely to yield a positive result (<2% probability) except for melanoma cases with a strong family history of melanoma, those who have had three or more primary tumours, and individuals with more than one primary tumour and who also have other affected family members, where the overall prevalence of mutations is estimated to be approximately 25%, 30% and 24% respectively. The gene discussed is CDKN2A; the disease is neoplasm.