The incidences of malignant melanoma recorded by 59 population-based cancer 
registries were investigated to determine the effects of racial and skin-colour 
differences. White populations exhibited a wide range of melanoma incidences and 
females commonly, though not invariably, had a higher incidence than males. 
Non-white populations experienced in general a much lower incidence of melanoma 
although there was some overlap of white and non-white rates. No predominant sex 
difference emerged among non-whites. Populations of African descent were found 
to have a higher incidence than those of Asiatic origin, but it was concluded 
that this was due largely to the high frequency of tumours among Africans on the 
sole of the foot. A clear negative correlation between degree of skin 
pigmentation and melanoma incidence emerged for the exposed body sites. These 
data provide strong support for the hypotheses that UV radiation is a major 
cause of malignant melanoma and that melanin pigmentation protects against it. 
Further research is required to elucidate the aetiology of melanoma of the sole 
of the foot.