Married individuals tend to be heavier than those who are unmarried, particularly men, and individuals in different ethnic categories vary in their involvement in marriage and in their body weights. We examined gender and ethnic differences in relationships between marital status and body weight using cross-sectional data from the 1999-2002 National Health and Nutrition Examination Survey (NHANES) for 3,947 women and 4,019 men. The findings revealed that compared to married men in the same ethnic category, white divorced men, black never-married men, and all Hispanic men except for widows had lower odds of being overweight. Compared to married women in the same ethnic category, white women's weights did not significantly differ by marital status, black separated women had greater odds of being overweight, and Hispanic never-married women had lower odds of being overweight. Associations of marriage with body weight appear to be at least partly contingent upon gender and ethnicity, which may reflect larger societal patterns of involvement in marriage, commitment to family, and body-weight norms and expectations.