Between 6 and 14% of malignant melanomas have been reported to occur in a familial pattern. In this study 785 melanoma patients from the Victorian Melanoma Service and the private practice of a dermatologist were assessed for the total number of melanocytic naevi, the number of dysplastic naevi and other clinical characteristics categorized according to whether there was a family history of melanoma. It was found that the presence of 100 or more naevi, six or more dysplastic naevi and blue eyes in a patient with melanoma were significantly associated with a family history of melanoma. Patients with two or more family members with melanoma were significantly more likely to develop melanoma at a younger age and to develop multiple melanomas. This study concludes that large numbers of melanocytic naevi and dysplastic naevi in melanoma patients are useful characteristics in practice to identify patients at risk of familial occurrence of melanoma. Family members of these patients should receive a medical assessment for their pigmented lesions.