A double-blind placebo-controlled study of 5-HTP and clomipramine was carried out on 45 patients suffering from anxiety disorders (DSM-III). Clomipramine has shown to be effective in that it induced significant improvement on all rating scales as compared to placebo. 5-HTP showed a moderate reduction of the symptomatology on the 90-item symptoms checklist (SCL-90) and the State Scale of the Spielberger State-Trait Anxiety Inventory. Clomipramine and 5-HTP differed in their efficacy in that 5-HTP did not affect the associated depressive symptomatology. The results support the hypothesis that brain serotonergic pathways are involved in the pathogenesis of anxiety disorders, particularly in agoraphobia and panic disorders.