The FAMMM syndrome consists of the familial occurrence of cutaneous malignant melanoma and atypical nevi (dysplastic nevi), and is inherited as an autosomal dominant trait. Conflicting results have been reported on the question of whether the syndrome includes increased susceptibility to non-melanoma cancers. We have studied cancer of all anatomic sites and histologies in nine FAMMM families which were ascertained in a pigmented lesions clinic in the Netherlands. We evaluated two hypotheses: that the number of systemic cancers observed in the families was excessive, compared to expected incidence, based on Dutch incidence data, and that there was variation (or heterogeneity) among families in the frequency of systemic cancer. A significant excess of systemic cancer (especially digestive tract cancer) was observed. Significant heterogeneity was also found among the families; three of the nine families had marked excess in numbers of systemic cancers, and the remaining families had normal numbers of cancers among the known FAMMM gene carriers and their first degree relatives. Thus, we provide evidence of increased susceptibility to systemic cancer occurring in conjunction with the FAMMM syndrome in a subset of this resource.