This article reviews efficacy studies of the reversible selective inhibitor of monoamine oxidase A (MAO-A) moclobemide, which has now received extensive evaluation. Placebo-controlled trials have shown it clearly to be effective. In comparisons with tricyclic and similar antidepressants and with serotonin reuptake inhibitors, it has been found of equal efficacy to these standard drugs. Because of previous suggestions that older MAO inhibitors are particularly effective in depressions characterized as atypical, the effects in subtypes are of particular interest. The evidence indicates that moclobemide is effective in typical severe depression with melancholia rather than being limited to less typical subtypes.