In children with steroid-resistant nephrotic syndrome (SRNS) hyperlipidaemia may in the long term be associated with progressive renal insufficiency and increased risk of coronary heart disease. We have assessed the efficacy and tolerability of diet prior to and in combination with a hydroxymethylglutaryl CoA reductase inhibitor, simvastatin, in seven children with SRNS with a mean age of 8 years (range 1.8-16.3 years). Dietary advice to maintain adequate energy and protein intakes with reduced saturated fat and cholesterol intake had little impact on lipid levels pre treatment (mean reduction in cholesterol 1 mmol/l, triglyceride 1.1 mmol/l) but was maintained throughout the study duration. The mean cholesterol and triglyceride concentrations pre treatment were 12.1 +/- 2 (SEM) mmol/l and 8 +/- 2.1 (SEM) mmol/l, respectively. On a median simvastatin dose of 10 mg/day (range 5-40 mg) there was a 41% reduction in cholesterol to 6.6 +/- 0.77 (SEM) mmol/l and a 44% reduction in triglyceride to 3.9 +/- 1.38 (SEM) mmol/l at 6 months which was sustained at 12 months in five patients. The drug was well tolerated with no clinical side effects being noted. Over 6 months the mean plasma albumin concentrations increased from 18.2 +/- 1.26 (SEM) g/l to 23 +/- 2.51 (SEM) g/l, accounted for by three patients (1 complete remission, 1 partial remission, 1 end-stage renal failure). Plasma creatinine concentrations remained stable in five patients with two having progressive chronic renal failure. Growth parameters for both weight and height were maintained. Simvastatin has a beneficial effect on abnormal lipid levels in SRNS but the effectiveness of long-term therapy needs to be evaluated.