Medical management of the agitation associated with acquired brain injury (ABI) has been proble matic. At least 12 distinct drugs are currently recommended in the medical literature. In recent years, on the ABI in-patient rehabilitation unit, methotrimeprazine (MTZ) has come to be the preferred drug and is used routinely for effective treatment of agitation. The objective of this paper is to describe the use and safety of MTZ in the rehabilitation of ABI patients. A retrospective chart review of all patients discharged from the ABI unit over a course of 2 years was conducted. In addition to demographics such a aetiology of ABI, sex, age, length of stay, Glasgow Coma Scale, length of posttraumatic amnesia and others, a detailed analysis was made of the multidisciplinary progress notes to determine the daily agitation status and the daily use of psychotropic medication. All notes on side effects and adverse reactions were carefully documeneted. 120 first admission recent ABI patients were discharged in the 2 year study period. Of these, 69 (57%) had some level of agitation and 56 (48%) were treated with MTZ, in doses of 2-50 mg up to four times daily. Agitation was controlled in most cases. In only two cases were significant side effects noted. While MTZ has been used as a safe and effective neuroleptic in psychiatry for over 40 years, this is the first report of its use in treating agitation in ABI.