A relative bioavailability study of conventional tablet of propranolol hydrochloride was conducted in a group of 18 healthy volunteers employing the innovator's product as the reference tablet formation. Based on plasma levels of propranolol for the 24 h following administration of 2 x 40 mg oral propranolol hydrochloride tablets, the relative extent of availability was shown to be 100.8 per cent for the test tablet formulation; no significant differences were detected between formulations with respect to any of the pharmacokinetic parameters examined. Large intersubject variations in plasma propranolol concentrations and the subsequently calculated areas under the plasma concentration/time curves were attributed to substantial presystemic biotransformation differences.