The relationship between cutaneous malignant melanoma and possible host factors was investigated in a population-based case-control study from East Denmark over a 3-year period. A total of 474 melanoma patients and 926 population controls aged 20-79 years were interviewed. Patients with lentigo maligna melanoma were not included. The major constitutional risk factors were: number of raised naevi on the arms (RR = 5.1 for 5+ vs. none), degree of freckling (RR = 2.9 for many vs. none), and light hair colour (RR = 1.7 for blond/fair vs. dark brown/black), which were independent of one another. An apparent synergy between number of raised naevi on the arms and degree of freckling was found. Thus, persons at high risk of melanoma may be identified by a simple assessment of naevi and degree of freckling. No significant difference was found between superficial spreading melanoma and nodular melanoma with regard to the most important host factors.