Forty-one patients meeting DSM-III criteria for social phobia completed a randomized comparative trial of the monoamine oxidase inhibitor phenelzine, the cardioselective beta-adrenergic blocker atenolol, and placebo. No significant differences were seen after 4 weeks of treatment in this preliminary trial. At the end of 8 weeks, however, phenelzine demonstrated greater efficacy than atenolol or placebo on dimensional ratings of overall severity of social phobia. No atenolol-placebo differences were observed. The authors shall present maintenance and discontinuation findings in a final report. Phenelzine may act in patients with social phobia by directly reducing interpersonal hypersensitivity.