The tolerability of epanolol, a new antianginal agent given as a single daily oral dose of 200mg, has been compared with the oral formulation of metoprolol (100mg twice daily) in a multicentre, randomised, double-blind, crossover study in 573 patients with stable angina (VISA 1). Patient preference for treatment was determined and efficacy was also monitored. Four weeks' treatment with one agent was followed by 4 weeks' treatment with the alternative agent. At the end of the study, patients were asked to express a preference, where possible, for 1 of the 2 treatments. The preliminary results of the study show that the preference question was answered by 524 patients (91.9%), and although 30 more patients preferred epanolol (45% preferred metoprolol, 55% preferred epanolol), the trend did not reach statistical significance (p = 0.137). Reasons for preference for epanolol were largely based on patients having fewer adverse effects, with fewer angina attacks and a general improvement in well-being as secondary reasons. Reasons for preference for metoprolol, however, were evenly divided between fewer adverse effects and fewer angina attacks, with a general improvement in well-being of less importance. Responses to a tolerability questionnaire consisting of 43 questions on 7 different body systems showed that epanolol had a significantly better profile than metoprolol for 10 of the side effects, particularly those associated with beta-blocker treatment. Responses to only one question indicated that patients tolerated metoprolol better than epanolol. Two patients died during the study (one on metoprolol treatment and one on epanolol treatment). Neither death was attributed to the study treatment.(ABSTRACT TRUNCATED AT 250 WORDS)