A prospective 3‐year epidemiological study, from 1986 to 1988, of malignant melanoma (MM) in West Glamorgan has shown an increase in the number of patients presenting with this condition associated with a significant trend towards thinner lesions. A total of 116 cases was recorded with an annual crude incidence per 100000 population of 7·4 for males, 13·7 for females and 10·6 overall. Although the numbers are relatively small and must he interpreted with caution, these are the highest incidence rates for MM recorded to date in the United Kingdom. These figures are almost double those recorded by the Welsh Cancer Registry for West Glamorgan (1979–83), wherein the corresponding rates recorded were 3·8 for males, 7·4 for females and 5·6 overall. The mean age of diagnosis was 56·9 years for males and 57 years for females. The mean depth of invasion measured on the Breslow scale was 2·68 mm for males and 1·55 mm for females. There was no change in depth of invasion for males, which was consistently higher than in females throughout, the mean depth being 2·77 mm in 1986 and 2·74 mm in 1988 for males, and 2·00 mm in 1986 and 1·36 mm in 1988 for females. Over all there was a statistically significant trend towards thinner lesions over the 3‐year period. Copyright © 1990, Wiley Blackwell. All rights reserved
