Epidemiological studies in human show that size in early life is related to blood cholesterol concentrations in adult life, raising the hypothesis that early nutrition programs later lipid metabolism, affecting risk for later vascular disease. Here, we tested the hypothesis that nutrition during pregnancy or lactation in the rat programs lipid metabolism in the offspring, studied in adult life (mean 6 months). Rats (n 35) from normally-fed dams (controls) were compared with (1) rats (n 22) from dams protein-restricted in pregnancy and lactation; (2) rats (n 9) born to normally-fed mother crossed to protein-restricted lactating dams and (3) those (n 9) born of protein-restricted dams and crossed to normally-fed lactating animals. In these latter three groups the offspring showed long-term reduction in plasma cholesterol, HDL-cholesterol and triacylglycerol concentrations compared with controls. The effects were predominantly in males. These findings suggest that in the rat the sensitive period for nutritional programming of cholesterol and triacylglycerol metabolism is both pre- and postnatal (pre-weaning) and that rats may be 'indirectly' programmed by altering the maternal nutritional milieu during gestation or lactation. Whilst it has been hypothesized that early human undernutrition programs risk for vascular disease, one aspect of undernutrition, low maternal protein intake, in this rat model programmed lower plasma cholesterol and triacylglycerol concentrations.