Combination therapy is routinely used to achieve improved cholesterol reduction in familial hypercholesterolaemia. We compared the standard simvastatin plus bile-acid sequestrant (cholestyramine) therapy with simvastatin plus fenofibrate in 29 patients with severe familial hypercholesterolaemia. The fibrate regimen resulted in an 35.1 +/- 10.7% reduction in total cholesterol, a 40.6 +/- 20.5% in LDL cholesterol, 17.2 +/- 56.5% reduction in triglycerides and a 20.3 +/- 52.0% increase in HDL cholesterol. The cholestyramine regimen produced reductions of 29.3 +/- 13.2% in cholesterol, 37.1 +/- 21.9% in LDL cholesterol, and 12.5 +/- 48.9% in triglycerides, and a 5.0 +/- 25.4% rise in HDL cholesterol. The fibrate regimen was significantly more effective in reducing total cholesterol (p < 0.001) and LDL-cholesterol (p = 0.004), and also reduced triglycerides significantly (p = 0.05), compared to the cholestyramine regimen. There were significant improvements in the LDL:HDL cholesterol ratio (3.62 +/- 1.54 vs. 4.00 +/- 1.36; p = 0.05) and in the apolipoprotein B:A1 ratio (1.13 +/- 0.036 vs. 1.20 +/- 0.34; p = 0.05). Gastrointestinal side-effects occurred in 10 patients on cholestyramine therapy, and four patients on fibrate therapy had myalgia. There were no cases of rhabdomyolysis with either regime. No significant differences in liver biochemistry or creatine kinase were seen with either regimen.