People with acute psychotic illnesses, especially when associated with agitated or violent behaviour, may require urgent pharmacological tranquillisation or sedation. Droperidol, a butyrophenone neuroleptic, is used for this purpose in several countries.To estimate the effects of droperidol when compared to other treatments for controlling disturbed behaviour and reducing psychotic symptoms for people with suspected acute psychotic illnesses.The Cochrane Controlled Trials Register (Issue 2, 2000), The Cochrane Schizophrenia Group's Register (May 2000), EMBASE (1980-2000), MEDLINE (1966-2000), PASCAL (1973-2000) and PsycLIT (1970-2000) were methodically searched. Twenty-one other databases were also searched as part of a broader project and this composite database was searched for this review. This was supplemented by hand searching reference lists, contacting industry and relevant authors.Randomised clinical trials comparing droperidol to any treatment, for people with suspected acute psychotic illnesses, such as schizophrenia, schizoaffective disorder, mixed affective disorders, manic phase of bipolar disorder or brief psychotic episode.Studies were reliably selected, quality assessed and data extracted. Data were excluded where more than 50% of participants were lost to follow up. For binary outcomes, standard estimations of risk ratio (RR) and their 95% confidence intervals (CI) were calculated. Where possible, weighted number needed to treat or harm statistics (NNT, NNH), and their 95% confidence intervals (CI), were also calculated.Only two clearly relevant randomised trials with usable data were identified. One additional study was included but focused on outcomes at 30 days rather than a few hours. One small (n=41) randomised trial compared droperidol (10mg IV) with placebo IV and found that people allocated to droperidol were significantly less likely to need additional haloperidol injections in the first few minutes (n=41, RR 0.37 CI 0.2 to 0.7, NNT 2 CI 1 to 10) than those given placebo. By 90 minutes this difference was still evident but not statistically significant (RR 0.46 CI 0.2 to 1.2). When 5mg IM droperidol was compared to 5mg IM haloperidol people given droperidol were again less likely to need additional injections by 30 minutes, than those given haloperidol, but this result did not quite reach conventional levels of statistical significance (n=27, RR 0.45 CI 0.2 to 1.01). One person out of 16 given haloperidol experienced a mild dystonic reaction, and none of the 11 people allocated to droperidol were reported to have experienced adverse effects.This is an important and surprisingly under-researched area. Use of droperidol for the emergency situation is currently justified on experience rather than evidence from well conducted and reported randomised trials.