The effect of once daily administration of sustained release capsules of propranolol 160 mg was compared with treatment with standard 40 mg tablets four times daily, in eight patients with stable angina pectoris, in a four week, double blind crossover, random treatment-order trial. Clinical evaluation and submaximal bicycle ergometry were performed before propranolol therapy and on the last day of each treatment period. Serum propranolol concentration over a 24 hour period on those two days ranged from 34.4 to 65.5 ng/ml for the tablets, and 27.7–76.0 ng/ml for the capsules. The peak increase in heart rate on exercise fell from 59 beats per minute to 43 and 41 bpm following the tablets and capsules, respectively (p<0.05). the="" degree="" of="" st="" segment="" depression="" decreased="" from="" 1.94="" mm="" to="" 0.94="" mm="" and="" 0.63="" mm,="" respectively=""><0.05). serum="" propranolol="" concentrations="" were="" significantly="" correlated="" with="" the="" reduction="" in="" peak="" heart="" rate="" (r="0.58,"><0.05), and="" in="" heart="" rate-pressure="" product="" (r="0.83,"><0.01). clinical="" attacks="" and="" nitroglycerin="" requirements="" were="" equally="" reduced="" by="" both="" formulations.="" sustained="" release="" capsules="" of="" propranolol="" 160="" mg="" given="" once="" daily="" were="" as="" effective="" as="" standard="" 40="" mg="" tablets="" given="" four="" times="" daily="" in="" the="" treatment="" of="" stable="" angina="" pectoris="" in="" patients="" requiring="" this="" dose="">