To assess the influence of depressive symptoms (defined using the CES-D) on weight change, we analysed data from 1794 adults, aged 25-74 years, who participated in the first National Health and Nutrition Examination Survey in 1971-1975 and the National Health Epidemiologic Follow-up Study in 1982-1984. After adjusting for baseline covariates using multiple linear regression, the data show that younger men (< 55 years) who were depressed at baseline gained nearly 3 kg more over the follow-up period than those who were not depressed. Among these younger men, however, education modified the effect of depression on weight change; those with < 12 years of education gained more weight with depression than those with more education (6.2 vs. 1.2 kg, respectively; P < or = 0.01). In contrast, depressed younger women gained slightly less weight than those who were not depressed. Among younger women, education also modified the effects of depression on weight change; those with < 12 years of education gained less weight with depression than those with more education (-3.2 vs. 0.6 kg, respectively; P < or = 0.01). Among older people (> or = 55 years), both men and women who were depressed lost more weight than those who were not depressed. Depression may play a substantial role in the patterns of weight change among adults in the United States. These patterns of weight change may contribute to the adverse health effects associated with depression.