The effects of xamoterol (200 mg twice a day) in 21 patients with left ventricular dysfunction were studied in a double blind, randomised, crossover, placebo controlled trial with treatment periods of four weeks. Most patients had moderate heart failure (New York Heart Association class II), all had ischaemic heart disease, a history of a myocardial infarction, and symptoms of dyspnoea on exertion. Patients were assessed in terms of exercise duration (bicycle ergometer), clinical signs of heart failure, symptoms and activities, and ejection fraction. Xamoterol increased exercise duration (mean (SD] (from 445 (8) seconds to 484 (8) seconds) and ejection fraction (from 41.9 (1.3)% to 46.6 (1.3)%) and reduced the signs and symptoms of heart failure. The results of this study show that xamoterol is a safe and effective treatment for left ventricular dysfunction resulting from ischaemic heart disease.