It has been shown that cocaine given in the diet is able to reduce fat accumulation in the liver of protein-malnourished rats (Arch. Latinoamer. Nutr. 19: 69-79, 1969). This study was, therefore, designed to approach the probable action of the drug upon the process (increased triglycerides synthesis and normal/decreased capacity for exporting triglycerides from the liver into the blood) which leads to an increased fat accumulation in the liver under this physiological condition. To accomplish this purpose, the total and fractioned lipids in the liver and total lipids as well as lipoproteins in serum were determined in female Wistar rats (120-130 g) fed either a 5% corn protein diet or a 20% casein diet, with and without cocaine (15 mg HCl cocaine/10 g of diet) for 18 days. The results, aside from confirming the reduction (p less than 0.001) of fat accumulation in the liver of rats fed on the 5% corn protein diet plus cocaine, revealed that this drug also reduced triglycerides concentration (significantly, (p less than 0.001, when results were calculated by difference, and slightly reduced them when results were determined) in this tissue. Nevertheless, it increases both total lipids (p less than 0.05) and triglycerides-rich pre-beta lipoprotein (p less than 0.10) levels in the serum of these animals. Otherwise, these lipidic parameters were not modified by cocaine in rats on the 20% casein diet, except for the total cholesterol level in liver and the cholesterol-rich beta lipoprotein level in serum. Respectively, these were slightly and significantly (p less than 0.001) reduced by the drug. These evidences and their statistical significance suggest that cocaine given chronically with the 5% corn-protein diet for 18 days, reduces at least partially (other biochemical event in the liver could have also accounted for its effect at this level) the liver fat accumulation, by increasing the triglycerides output from the liver into the blood. Elsewhere, cocaine appears to be able to induce some metabolic alterations in the hepatic cholesterol of well-nourished rats.