To study the effect of renal function on the development of lipid and apolipoprotein abnormalities in human renal disease, we have investigated 75 patients at different stages of renal insufficiency. The patient population consisted of 19 patients with less advanced renal failure (CRF:1) characterized by a mean glomerular filtration rate (GFR) of 37.4 ± 14 ml/min, 31 patients with advanced renal failure (CRF:2) having a mean GFR value of 7.9 ± 7.3 ml/ min and 25 patients on maintenance hemodialysis (CRF:HD). Patients in the CRF:1 group had normal plasma triglyceride (TG) and total cholesterol (TC) levels. In the CRF:2 and CRF:HD group, TG levels were increased two -to threefold, together with a moderate elevation of TC levels. All patient groups had elevated levels of VLDL cholesterol and slightly decreased levels of HDL cholesterol. The apolipoprotein profile of all patient groups was characterized by significantly reduced levels of apolipoprotein (Apo)A-I and ApoA-II and significantly increased levels of ApoC-III. CRF:2 and CRF:HD patients had also moderately elevated levels of ApoB, ApoC-I and ApoC-II. Levels of ApoE were only elevated in CRF:HD patients. All patients, regardless of TG levels, had significantly lower ApoA-I/ApoC-III ratios than controls. GFR was positively correlated with ApoA-I and inversely correlated with TC, TG and ApoC-III. CRF:HD patients had slightly higher ApoA-I and ApoA-II and lower ApoB levels compared to CRF:2 patients. Patients with vascular disease had higher TC, TG, ApoB, ApoC-II and ApoE than patients without vascular disease. These results demonstrate that the dyslipoproteinemia with CRF is already manifested at the early stages of disease through its abnormal apolipoprotein rather than lipid profile.