Despite its poorly described pharmacology, effectiveness, and safety, use of St. John's wort (SJW) is largely unsupervised and unexplored, and can potentially lead to adverse outcomes. We conducted a telephone survey of 43 subjects who had taken SJW to assess demographics, psychiatric and medical conditions, dosage, duration of use, reason for use, side effects, concomitant drugs, professional consultation, effectiveness, relapse, and withdrawal effects. Most subjects reported taking SJW for depression, and 74% did not seek medical advice. Mean dosage was 475.6+/-360 mg/day (range 300-1200 mg/day) and mean duration of therapy was 7.3+/-10.1 weeks (range 1 day-5 yrs). Among 36 (84%) reporting improvement, 18 (50%) had a psychiatric diagnosis. Twenty (47%) reported side effects, resulting in discontinuation in five (12%) and one emergency room visit. Two consumers experienced symptoms of serotonin syndrome and three reported food-drug interactions. Thirteen consumers experienced withdrawal symptoms and two had a depressive relapse. These data suggest the need for greater consumer and provider awareness of the potential risks of SJW in self-care of depression and related syndromes.