This population-based case-control study systematically examined reported malignant melanoma risk factors by anatomic site. Study subjects consisted of 548 invasive melanoma cases diagnosed in Connecticut during 1987-1989 and 494 randomly selected controls. Multivariate polychotomous logistic regression was used to determine whether risk factors differed across anatomic sites. Risk factors examined included demographic and pigmentary characteristics, sun exposure-related factors, anatomic site-specific sunburn, recreational water activity clothing habits and number of nevi. A pattern of site-specificity w a s observed for sunburn. A history of sunburn at an anatomic site was specifically related to the development of malignant melanoma at that site more so than at other sites. This sitespecificity was consistent with a direct role for intense, intermittent sun exposure in the development of melanoma. Age and gender were the only risk factors that differed significantly in effect across anatomic sites. The age difference was explained by differences in histologic subtype across sites. The gender difference could not be explained by sex differences in anatomic site-specific sunburns or in recreational water activity clothing habits. Alternative explanations include sex differences in behavioral patterns of sun exposure that we did not measure and as yet unelucidated differences in susceptibility to melanoma according to sex and anatomic site.o 1996 Wiley-Liss, Inc.The determinants of the anatomic site distribution of cutaneous malignant melanoma are not well understood. Descriptive studies of malignant melanoma time trends have shown significant anatomic site and gender differences (Chen et al., 1994;Dennis et al., 1993;Thorn et al., 1990). These differences have generally been attributed to anatomic siteand gender-specific differences in time trends in patterns of sun exposure, a consequence of changes in clothing fashions and recreational habits. However, only a limited number of analytical epidemiologic studies have examined malignant melanoma risk factors by anatomic site (Elwood et al., 1984; Green et al., 1986;Swerdlow et al., 1986; Holman et a/., 1986;Weinstock et al., 1989Weinstock et al., , 1991Kruger et al., 1992;Cress et al., 1995). Most examined only a small number of risk factors, and only 1 (Elwood et al., 1984) tested the statistical significance of differences across anatomic sites.The current investigation systematically examined reported malignant melanoma risk factors by anatomic site using data from a population-based case-control study. The major hypothesis was that the risk of malignant melanoma would vary across anatomic sites according to site-specific sun exposure and clothing habits, while host-related risk factors (e.g., sex, age, skin color, tanning ability) would not differ across anatomic sites.been interviewed as part of a case-control study of skin examination and lethal melanoma (Benvick et al., 1996).All incident first primary cases of cutaneous malignant melanoma (invasive and...