A total of 96 patients with moderate elevations of low-density lipoprotein (LDL) cholesterol were randomly assigned to 4 different double-blind treatment regimens: placebo; colestipol 5 g and lovastatin 20 mg/day (C5 + L20); colestipol 10 g and lovastatin 20 mg/day (C10 + L20); and lovastatin 40 mg/day (L40). During 12 weeks of therapy, C10 + L20 achieved the greatest reduction in total cholesterol (-32%) and LDL cholesterol (-48%) levels from baseline. This combination also exhibited significantly greater reductions in LDL cholesterol levels than the C5 + L20 and L40 groups (p < 0.01). The differences in total and LDL cholesterol reduction between the C5 + L20 and L40 groups were not significant. Similar changes and differences between treatments were seen in apolipoprotein B levels. Whereas mean total apolipoprotein A-I levels increased with all treatments (p < 0.05), lipoprotein particles A-I were significantly increased in the C10 + L20 group (p < 0.01) only. Results demonstrate that the combination of low-dose lovastatin (20 mg/day) with low-dose colestipol (5 or 10 g/day) produces LDL cholesterol reductions equal to or greater than higher doses of lovastatin (40 mg/day). In addition, low-dose combinations are > 25% more cost-effective than high-dose monotherapy.