Parent-child, sibling, and spouse similarities in Health-Carter somatotype components are considered in 938 individuals from 243 nuclear families of French Canadian ancestry. Familial correlations were considered for each somatotype component, after adjusting for age, gender, and the other somatotype components. Correlations were also calculated with and without adjustment for energy intake (EI) and physical activity level (AL). AL and EI were estimated from 3-day records, including a weekend day. Age and gender accounted for a significant (P < 0.01) proportion of variation in somatotype components of parents and children. The addition of AL and EI to age and gender in the regression analysis increased the variance explained by 11% (children) and 18% (adults) for endomorphy, 6% (children) and 8% (adults) for mesomorphy, and 11% (children) and 20% (adults) for ectomorphy. Spouse correlations for somatotype components were low and not significant. Parent-child and sibling correlations were significant and ranged from 0.18 to 0.48 for endomorphy, 0.23 to 0.59 for mesomorphy, and 0.14 to 0.47 for ectomorphy. Adjusting for AL and EI did not appreciably influence the familial correlations. Parent-offspring and sibling correlations showed familial aggregation for mesomorphy, while correlations for endomorphy and ectomorphy were lower. These results are consistent with a transmission effect across generations and, perhaps heritability, with the level being highest for mesomorphy. © 1993 Wiley-Liss, Inc.