Thirty patients with thyrotoxicosis were randomly divided into 3 groups of ten which were treated for 8 weeks with either practolol, propranolol or placebo. The pills were administered in a double blind manner and the investigator had the option of doubling the dose at each visit. Propranolol and practolol were equally effective, and better than placebo, at relieving the patients general well-being as well as the tachycardia, subjective and objective tremor, skin warmness and moistness and the intensity of the thyroid bruit.