In a randomized, controlled, double-blind trial, 70 patients (mean age, 49.7 years) suffering from mild to moderate depression received one tablet of either St. John's Wort (Hypericum perforatum) extract (Calmigen) or fluoxetine hydrochloride (Prozac) twice a day for 6 weeks. Efficacy was determined according to the 17-item Hamilton Rating Scale for Depression (HAMD), the von Zerssen depression scale (DS), Clinical Global Impression (CGI), and patients' overall evaluation. Significant decreases (P<.001) of 50% in the Hypericum group and 58% in the fluoxetine group in the HAMD score and of 42% and 52% on the DS spoke to the efficacy of both medications. The Hypericum extract achieved 83% of the efficacy of fluoxetine on the HAMD and 78% on the DS. Assessments by physicians (CGI) and patients indicated considerable improvement with no between-treatment differences. Of the 9 dropouts (13%), 2 in the Hypericum group and 2 in the fluoxetine group were due to adverse reactions. Safety evaluations demonstrated only minor changes. The Hypericum preparation tested in this study is therapeutically equivalent to fluoxetine and is therefore a rational alternative to synthetic antidepressants.