In a study of risk factors for the development of melanocytic naevi in relation to the pathogenesis of malignant melanoma 197 white adults were examined by four dermatologists and naevus counts correlated with several other features. Highly significant associations were found between large numbers of banal acquired melanocytic naevi and the ability to tan easily without burning (skin types 3 and 4; relative risk 4.6), brown or hazel eyes (relative risk 3.5), green or grey eyes (relative risk 3.5) and brown or black hair (relative risk 3.7). No significant associations with numbers of naevi were shown for parity or use of oral contraceptives or other steroid hormones. This is the first study to find any relation between melanocytic naevi and phenotypic factors in a white population.