About 700 new cases of malignant melanoma of the skin are registered annually in Denmark. The incidence is increasing rapidly and the number of new cases increases by more than 5% per annum. The most important phenotypical risk factors are the number of acquired pigmented naevi and exposure to sunlight is the most important risk factor in the external environment so that severe sunburn in children and intermittent intense exposure to sunlight increase the risk of melanoma. The thickness of the tumour at the time of the diagnosis is the most important prognostic factor. The prognosis deteriorates with increasing thickness. Treatment is primarily surgical. In cases of inoperable local melanoma and regional recurrences, irradiation may be administered. Chemotherapy and/or immunotherapy are of experimental character. In the light of the rapidly increasing incidence, it is important that knowledge of risk factors for development of the disease and the clinical characteristics of early melanoma is spread to not only the medical profession but also to the general public.