Trazodone possesses a different pharmacological profile from that of conventional antidepressants. It is not a monoamine oxidase inhibitor, and it is not active in the major behavioral tests used to identify antidepressant activity. In addition to its antidepressant activity, the behavioral pharmacology of trazodone includes analgesic, antianxiety, and sedative components. The significant biochemical actions of trazodone are selective inhibition of 5-hydroxytryptamine (5-HT) uptake and interaction with 5-HT2 binding sites. It is not yet known if those two phenomena are related or even clinically relevant. However, in view of the time course of trazodone's action, it would seem that these selective effects following chronic administration may constitute its mechanism of antidepressant action.