The aim of the study was to assess the completeness and accuracy of cancer registration for cutaneous malignant melanoma. The study was conducted in seven health districts in England and one health board in Scotland from 1987 to 1989 with a total resident population of 3.6 million. Records from pigmented lesion clinics and pathology laboratories collected during the Cancer Research Campaign's health education programme to promote the early detection of melanoma were matched with cancer registrations from a total of five regional cancer registries. In England 74% out of a total of 642 cases of invasive malignant melanomas (ICD 172) and 44% out of a total of 155 in situ melanomas (ICD 232) had been registered compared with 96% and 100% respectively in Scotland. A significantly higher proportion of late-stage cases was found among registered than among non-registered cases in England (P < 0.001). In all registries the majority of superficial spreading in situ melanomas were miscoded as invasive cases. The annual incidence of invasive malignant melanoma in the English study areas was found to be seven per 100,000 in men and 11 per 100,000 in women, similar to that reported in Scotland. The registries are best at recording thick or late-stage melanomas. As the skin cancer target for Health of the Nation depends on monitoring trends in the incidence of malignant melanoma, future improved ascertainment of cases and changes in the type of cases being registered must be taken into account.