Secular trends in the relationship of body mass index (BMI) and skinfold thickness to educational and income levels were examined for white and black men aged 18-34 y over the period 1960-80 with data from three successive national surveys: NHES Cycle I, NHANES I, and NHANES II. Statistical models were fitted to assess the variability in mean BMI over time within levels of education or income. There were few secular changes in mean BMI. In both white and black men a secular change from a slight positive association between mean BMI and education to a negative association was characterized chiefly by an increase in mean BMI at the lowest educational level. A slight positive association between income level and mean BMI persisted almost unchanged over this period. Mean BMI was similar for black and white men. These findings are compared and contrasted with those from a similar study for young women.