A series of [alpha-(heterocyclyl)benzyl]piperazines was synthesized and their effect of reducing serum cholesterol and triglyceride levels in the rat was evaluated. A systematic exploration of the structure-activity relationships led to the synthesis of (R,S)-(3,5-dimethylisoxazol-4-yl)[4-(1-methylethyl)phenyl] (4-methylpiperazin-1-yl)methane dihydrochloride (M&B 31 426), which had potent activity in lowering serum lipid levels at a daily oral dose of 2 mg/kg and was 100 times more potent than clofibrate.