OBJECTIVE: To systematically review placebo-controlled randomized trials of homeopathy for psychiatric conditions. DATA SOURCES: Eligible studies were identified using the following databases from database inception to April 2010: PubMed, CINAHL, PsycINFO, Hom-Inform, Cochrane CENTRAL, National Center for Complementary and Alternative Medicine grantee publications database, and ClinicalTrials.gov. Gray literature was also searched using Google, Google Scholar, the European Committee for Homeopathy, inquiries with homeopathic experts and manufacturers, and the bibliographic lists of included published studies and reviews. Search terms were as follows: (homeopath* or homoeopath*) and (placebo or sham) and (anxiety or panic or phobia or post-traumatic stress or PTSD or obsessive-compulsive disorder or fear or depress* or dysthym* or attention deficit hyperactivity or premenstrual syndrome or premenstrual disorder or premenstrual dysphoric disorder or traumatic brain injury or fibromyalgia or chronic fatigue syndrome or myalgic encephalitis or insomnia or sleep disturbance). Searches included only English-language literature that reported randomized controlled trials in humans. STUDY SELECTION: Trials were included if they met 7 criteria and were assessed for possible bias using the Scottish Intercollegiate Guidelines Network (SIGN) 50 guidelines. Overall assessments were made using the Grading of Recommendations Assessment, Development and Evaluation procedure. Identified studies were grouped into anxiety or stress, sleep or circadian rhythm complaints, premenstrual problems, attention-deficit/hyperactivity disorder, mild traumatic brain injury, and functional somatic syndromes. RESULTS: Twenty-five eligible studies were identified from an initial pool of 1,431. Study quality according to SIGN 50 criteria varied, with 6 assessed as good, 9 as fair, and 10 as poor. Outcome was unrelated to SIGN quality. Effect size could be calculated in 16 studies, and number needed to treat, in 10 studies. Efficacy was found for the functional somatic syndromes group (fibromyalgia and chronic fatigue syndrome), but not for anxiety or stress. For other disorders, homeopathy produced mixed effects. No placebo-controlled studies of depression were identified. Meaningful safety data were lacking in the reports, but the superficial findings suggested good tolerability of homeopathy. A funnel plot in 13 studies did not support publication bias (?(2)(1) = 1.923, P = .166). CONCLUSIONS: The database on studies of homeopathy and placebo in psychiatry is very limited, but results do not preclude the possibility of some benefit.