Treatment of 5 hypertriglyceridemic and 1 normolipemic patients with propranolol, a non-selective beta-blocking agent, and metoprolol, which is generally considered to be a cardioselective beta-blocking agent, and metoprolol, which is generally considered to be a cardioselective beta-adrenoceptor antagonist, produced a further elevation in their triglyceride levels. The subjects were followed for 20 wk, during which they received propranolol for 8 wk, a placebo for 4 wk and metoprolol for 8 wk in a crossover design. The analysis suggested that the increase in triglyceride levels was less pronounced with the more cardioselective agent. .alpha.-Cholesterol decreased significantly after propranolol but remained constant while on metoprolol. Both drugs decreased .beta.-cholesterol whereas chylo- and pre-.beta.-cholesterol increased, particularly with propranolol. Considering the contradictory evidence regarding the clinical importance of chronic elevation of plasma triglyceride and decreased .alpha.- and .beta.-cholesterol concentrations, it is suggested that a cardioselective drug would be presently preferable in hyperlipidemic subjects.