In a double-blind crossover study the beta-adrenergic blocking drug propranolol hydrochloride reduced symptoms in 17 of 26 patients with chronic anxiety disorders. Both somatic and psychic symptoms improved as judged by patient and observer ratings. The most frequent side effects (dizziness, fatigue, and insomnia) were difficult to distinguish from anxiety symptoms and were, for the most part, mild. The therapeutic and side effects observed suggested CNS activity of the drug. Although propranolol is of benefit to patients with anxiety, its efficacy, compared with that of other antianxiety drugs, has not been established.