We completed a single site, double-blind, placebo-controlled, parallel design study of quetiapine for hallucinations in PD. Thirty-one subjects with PD and prominent visual hallucinations and Mini-Mental State Examination score >21 were randomly assigned in a 2:1 drug to placebo ratio, up to 200 mg daily of quetiapine or matching placebo given in two doses. They were seen at 3 weeks (100 mg/day) and 12 weeks (200 mg/day, with optional dose reduction). Evaluation included the Unified Parkinson's Disease Rating Scale (UPDRS), the Baylor PD Hallucination Questionnaire, and a battery of neuropsychological tests. The demographics between subjects randomized to drug (n = 21) vs. placebo (n = 10) were similar. The final dose of active drug was 200 (n = 11), 150 (n = 2), 100 (n = 3), and 75 (n = 1) mg per day. All placebo subjects were on the equivalent of 200 mg per day. The UPDRS Activities of Daily Living and Motor scores did not significantly change compared to placebo. Compared to placebo, there were no significant changes in our hallucination questionnaire, the Brief Psychiatric Rating Scale (BPRS), or question 12 (hallucination item) of the BPRS. There were no significant changes on any of the neuropsychological measures. Adverse events on drug included sedation (n = 9), but no drug-related adverse events precipitated discontinuation and none were rated as serious. Quetiapine, up to 200 mg daily, was well tolerated and did not worsen UPDRS scores; however, there was no significant improvement in psychosis rating scales compared to placebo. Larger doses of drug and greater sample sizes might be considered in future studies.