In a double-blind, parallel group trial, 78 subjects with social phobia received moclobemide (a new reversible inhibitor of monoamine oxidase A) phenelzine, or placebo. After eight weeks, both active drugs-phenelzine somewhat more than moclobemide--were clinically and statistically significantly more effective than placebo, as assessed by rating scales. There was some further improvement between weeks 8 and 16, particularly in the moclobemide group; at week 16, 82% of the moclobemide and 91% of the phenelzine-treated patients were almost asymptomatic. Moclobemide was, however, much better tolerated than phenelzine. Patients withdrawn from active drugs had relapsed by week 24, providing additional support for the efficacy of the active drugs.