The pharmacokinetics of a sustained release (SR) propranolol (Betalong) were compared with conventional propranolol (Inderal) after single and multiple dosing in 8 normal healthy volunteers. The study was designed in a crossover fashion. SR propranolol 80 mg in a single dose maintained the plasma concentration of propranolol above the minimum therapeutic concentration up to 25 h. The steady-state propranolol concentration after 80 mg conventional propranolol twice daily and SR propranolol 80 mg daily was almost similar. The results indicate that Betalong (SR propranolol) satisfies the pharmacokinetic criteria expected of a sustained release preparation of propranolol and may be useful in single daily dose.