Ziprasidone is a novel antipsychotic which, in oral formulation, has been shown to be effective and well tolerated in the treatment of acute psychosis. This pilot study examined the efficacy and tolerability of the intramuscular (IM) formulation and the transition from IM to oral ziprasidone in patients with acute schizophrenia. The study design was an open, prospective, 5-day treatment trial of IM ziprasidone followed by oral dosing in 12 patients with acute exacerbation of schizophrenia. Various doses (2.5, 5, 10, or 20 mg) up to 60 mg/day total were administered over 3 days, followed by transition to oral ziprasidone on Days 4-5. All patients completed the study. Mean improvements between baseline and Day 3 were observed in Brief Psychiatric Rating Scale (47.8 to 28.9) and Clinical Global Impression of Severity (6.1 to 5.3), and improvements were maintained on Days 4 and 5. No extrapyramidal syndrome, acute dystonia, or serious adverse events were reported. In these patients, IM ziprasidone 20-60 mg/day reduced psychomotor agitation and other symptoms of psychosis. The transition from IM to oral ziprasidone was well tolerated. Copyright (C) 2000 John Wiley & Sons, Ltd.