The efficacy, safety, and tolerability of simvastatin (20 mg twice a day) in the treatment of hyperlipidaemia due to unremitting nephrotic syndrome was compared with that of cholestyramine (8 g twice a day) in a crossover trial in ten patients. Two patients were taken off the protocol, one because he could not tolerate cholestyramine and one because of non-compliance with the cholestyramine regimen. No clinical or laboratory adverse experiences were noticed during the study in the other eight patients. Simvastatin was significantly more effective than cholestyramine in reducing the hyperlipidaemia--it produced a 36% decrease in total cholesterol and a 39% decrease in low density (LDL)-cholesterol, whereas cholestyramine reduced total cholesterol by 8% and LDL-cholesterol by 19%. With simvastatin the apolipoprotein B level decreased by 30%, whereas the apolipoprotein A level increased by 10%.