Serum lipids were studied in 98 nonnephrotic patients with chronic renal failure at pre-dialysis, dialysis and post-transplant stages. Hypertriglyceridemia was observed in pre-dialysis patients, although its degree was a modest one as compared to the preceding occidental reports. This difference may be ascribed to an ethnic peculiarity, since Japanese patients have a diet richer in carbohydrate than their Caucasian counterparts (% carbohydrate/total calories of 70 vs. 54–58). Hypertriglyceridemia persisted in the hemodialysis group, while no elevation was observed in serum cholesterol level. Elevated serum cholesterol levels were found in post-transplant patients. 8 pre-dialysis patients were fed carbohydrate-rich (64% of total calories) and carbohydrate-poor (47%) diets, each for 1 week successively, while maintaining an isocaloric level of 1,800 cal and a similar polyunsaturated to saturated fatty acid ratio (0.90 vs. 0.76). Significant reduction in serum triglycerides (TG) took place due to a decrease in dietary carbohydrate, while the plasma extrahepatic and hepatic post-heparinic lipolytic activities (PHLAs) showed constant decreased levels throughout the diet therapy. This may be suggestive of a deranged TG metabolism present in all pre-dialysis patients studied, primarily because all the pre-diet PHLAs were low even though the serum TG levels were not necessarily elevated and secondarily, a carbohydrate-rich diet could not induce such a reactive elevation in extrahepatic PHLA as would normally be observed. In conclusion, hypertriglyceridemia in patients with chronic renal failure may be caused by potentially defective TG-clearing ability that becomes manifest by conventional carbohydrate-rich diet.