The lipid and lipoprotein profiles including apolipoprotein A1 and B100 are measured in 50 idiopathic nephrotic patients (males 26, females 24) with mean age of 32 + 13.6 yrs, serum creatinine 1.32 +/- 0.43 mg/dl compared with 50 age matched normal controls. The renal histology consist of IgM nephropathy 70 per cent, membranous 12 per cent, and IgA 2 per cent. The serum cholesterol, triglycerides, LDL- cholesterol, VLDL-cholesterol, apolipoprotein B (521.6 +/- 201.6, 291.4 +/- 156.2, 438.8 +/- 207.4, 58.3 +/- 31.2, 265.1 +/- 119.8) are statistically significantly higher than controls (p < 0.001). The HDL-cholesterol (30.2 +/- 16.1) is also significantly lower than controls (p < 0.001) but apolipoprotein A is not different from normal subjects. The most common hyperlipoprotein type is type IIb (66%), less common are type IIa (22%), IV (6%) and III (4%) respectively. There is no correlation between serum lipids, lipoproteins and urinary protein, serum albumin, and histological diagnosis. The ratio of cholesterol: HDL, LDL: HDL and Apo A1: B are all significantly higher than normal control (p < 0.001) and correlate with urinary protein levels. This study shows that the nephrotic patients who have persistent heavy proteinuria have dyslipidemia which is highly atherogenic and probably increases the incidence of coronary heart disease.