The bioequivalence of two different tablets and a solution, each containing 10 mg propranolol hydrochloride was studied in twelve healthy volunteers. Single oral doses of each preparation were administered at intervals of one week. Samples of blood for propranolol radioimmunoassay were taken up to 8 h after dosing. The plasma propranolol concentration at 0.5 h was significantly higher for the solution than for the two tablet formulations which did not differ significantly from each other at any sampling point. The area under the curve was similar for all three preparations. The study demonstrated that the three different preparations of propranolol were bioequivalent.