A double-blind, cross-over study was performed in 23 consecutive patients with unstable angina at rest in order to compare the efficacy of verapamil (480 mg/day) and propranolol (240 mg/day) in reducing the number of anginal crises and nitroglycerin (NTG) consumption. Twenty patients, 15 men and five women, mean age 59.7 (range 45-68) years completed the study. The mean daily number of attacks was 3.1 in the two-day run-in period and 2.9 in a subsequent two-day placebo period immediately preceding the treatment periods. Propranolol reduced the number of attacks to 1.6 (P less than 0.01 compared to the run-in and placebo periods). Verapamil reduced the crises to 0.2/day (P less than 0.01 compared to the run-in placebo and propranolol periods). The NTG consumption behaved in a similar way. Adverse reactions to verapamil were observed in two patients. Although there are objective difficulties in performing correct trials in these kinds of patients, the results of this study indicate the efficacy of verapamil in preventing anginal pains during the "warm phase' of the unstable form and stress the superiority of this calcium antagonist when compared to propranolol.