Ultra-violet radiation (UVR) in sunlight is thought to be the main cause of malignant melanoma in lightly-pigmented populations. Individuals with fair skin, fair hair, blue eyes and/or a tendency to burn rather than tan when exposed to the sun are at particularly high risk of melanoma and should be given special attention in primary prevention programmes. Intermittent exposure to the sun, as in recreational exposure, may be a more potent cause of melanoma than more continuous exposure. Primary prevention offers the best prospects for a substantial reduction in mortality from malignant melanoma. However, there is little evidence available to judge the effectiveness of primary prevention of melanoma through reduction of exposure to the sun. Education for reducing exposure to the sun is common in high-risk populations but has never been evaluated adequately. Mortality from melanoma could also possibly be reduced by earlier diagnosis through education or screening of high-risk groups. Regular screening of patients with the familial dysplastic naevus syndrome should reduce their mortality from melanoma.