The aim of this study was to examine familial patterns of plasma leptin levels and the potential association with cardiovascular risk factors in a population sample of African-American families recruited from metropolitan Chicago. The study included 68 mothers, 31 fathers, 143 daughters, and 119 sons, for a total of 361 individuals from 118 families. Leptin levels were adjusted for the effect of age separately for mothers, fathers, daughters, and sons. Residuals were then standardized before estimating familial correlation using the maximum-likelihood method available in SEGPATH. With the exception of height, plasma leptin level was strongly correlated with all measured anthropometric variables. Familial effect (i.e., heritability) of leptin levels was estimated as 39% in this population at high risk for over weight. A significant sex difference was observed, and most of the estimated familial effect may be attributed to genetic influences since the spouse correlation was not statistically different from zero. A strong nonshared environmental effect is also suggested, however.