OBJECTIVE: The primary purpose of this article is to review the existing literature concerning the therapeutic uses, adverse effects, and possible drug interactions of St. John's wort (Hypericum perforatum) as compared to other antidepressant medications. METHODS: Reference material was obtained through database searches with time restrictions of 1985 to the present. Studies selected were those written in the English language which compared the role of St. John's wort, tricyclic antidepressants, monoamine oxidase inhibitors, and serotonin-selective reuptake inhibitors in the treatment of depression. Other studies were selected based on their evaluation of the safety and efficacy of St. John's wort as an antidepressant for a minimum of four weeks. RESULTS: A review of existing literature recognized nine clinical trials that reported the efficacy of St. John's wort as compared to placebo and to other antidepressant medications. Of these nine, four controlled studies were chosen based upon their large patient populations and their consistency in brand and dosage of St. John's wort used. These four studies demonstrated that St. John's wort was as effective as other antidepressant medications and more effective than placebo, as the clinical symptoms of depression greatly decreased upon administration of H. perforatum. The side-effect profile of H. perforatum at this time appears to be superior to any current U.S.-approved antidepressant medication. CONCLUSIONS: From the existing literature, St. John's wort appears to be a safe and effective alternative in the treatment of depression. Tricylic antidepressants and monoamine oxidase inhibitors can produce serious cardiac side-effects, such as tachycardia and postural hypotension, and many unwanted anticholinergic side-effects, including dry mouth and constipation. St. John's wort has proven to be free of any cardiac, as well as anticholinergic, side-effects normally seen with antidepressant medications. Based upon limited studies, St. John's wort appears to be an acceptable alternative to traditional antidepressant therapy, although trials on a larger scale are warranted in this area. Hypericum is available to the lay public as an over-the-counter preparation and may be misused if not fully understood.