The effects of a large dose (2 mg/100 g body weight) of medroxyprogesterone acetate (MPA), restricted feeding (50% of normal intake) and their interaction were investigated on the serum and liver lipid and protein distribution in female rats. MPA increased serum cholesterol and triglyceride levels in rats on ad libitum food intake without having any effect in the animals on restricted diet. There was no statistical difference in the total serum protein or albumin levels among the groups. The serum levels of alpha and gamma globulin were significantly lower in the underfed rats. MPA increased the concentration of gamma globulin in well nourished rats but interacted with dietary restriction to further reduce the level of this protein in the undernourished animals. There was no difference in the levels of hepatic phospholipids or free cholesterol among groups, However, cholesterol ester and triglyceride levels in liver were significantly elevated in the MPA-treated group fed ad libitum. A similar increase was not found in underfed rats. This study indicates that MPA exerts significant effects on the distribution of serum and hepatic lipids and serum globulin levels and that the effects are dependent upon the nutritional status of the subject.