The pharmacology, pharmacodynamics, clinical efficacy, drug interactions, adverse effects, and dosage and administration of colesevelam hydrochloride are reviewed. Colesevelam hydrochloride is a nonabsorbed lipid-lowering agent approved for use alone or in combination with hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors for the reduction of low-density-lipoprotein (LDL) cholesterol in patients with primary hypercholesterolemia. Colesevelam forms nonabsorbable complexes with bile acids in the gastrointestinal (GI) tract, resulting in changes in plasma lipid levels, including total, LDL, and high-density-lipoprotein cholesterol and triglycerides. Colesevelam has been reported to be four to six times as potent as traditional bile acid sequestrants (BASs), perhaps because of its greater binding affinity for glycocholic acid. Unlike cholestyramine and colestipol, colesevelam appears to reduce LDL cholesterol in a dose-dependent manner. In clinical trials, colesevelam demonstrated efficacy either alone or in combination with HMG-CoA reductase inhibitors in the treatment of primary hypercholesterolemia. Combination therapy appeared to be more effective than monotherapy. Although infection, headache, and GI adverse effects have been reported for colesevelam, the rates do not differ significantly from those occurring with placebo. The constipation that typically hinders compliance with traditional BASs is minimal. In one study, the rate of compliance with colesevelam was 93%. There is little evidence of clinically significant interactions involving colesevelam. The maintenance dosage is three 625-mg tablets twice daily or six tablets once daily, taken with meals. Colesevelam provides an effective alternative to cholestyramine and colestipol while offering the potential for fewer adverse effects and better compliance. Studies are needed to directly compare colesevelam with traditional BASs.