Clonazepam, first used for seizure disorders, is now increasingly used to treat affective disorders. We summarize the use of clonazepam to improve the management of depression. Clonazepam is useful for treatment-resistant and/or protracted depression, as well as for acceleration of response to conventional antidepressants. Clonazepam is at this time recommended for use in combination with SSRIs (fluoxetine, fluvoxamine, sertraline) as an antidepressant, and should be used at a dosage of 2.5-6.0 mg/day. If clonazepam is effective, a response should be observed within 2-4 weeks. It is significantly more effective for unipolar than for bipolar depression. Low-dose, long-term treatment with clonazepam exhibits a prophylactic effect against recurrence of depression. Although the mechanism of action of clonazepam has not yet been established, some investigators have been suggested that it involves enhancement of anti-anxiety effects, anticonvulsant effects on subclinical epilepsy, increase in 5-HT/monoamine synthesis or decrease in 5-HT receptor sensitivity mediated through the GABA system, and regulate in GABA activity.