An intramuscular formulation of the atypical antipsychotic aripiprazole (Abilify) has been developed and is approved in the EU for use in agitation and disturbed behaviour associated with schizophrenia. In the US, it is approved for the treatment of agitation associated with schizophrenia or bipolar I disorder (manic or mixed). In large, well designed trials, intramuscular aripiprazole was an effective and generally well tolerated treatment for agitation associated with schizophrenia, schizoaffective disorder, schizophreniform disorder or bipolar I disorder. Intramuscular aripiprazole was more effective than placebo in these patient populations and was noninferior to intramuscular haloperidol in those with agitation associated with schizophrenia and its related disorders. Aripiprazole is associated with a low risk for extrapyramidal symptoms (EPS), cardiac effects, hyperprolactinaemia, weight gain and other metabolic disturbances. Head-to-head trials comparing intramuscular aripiprazole with other intramuscular atypical antipsychotics are required before the relative position of each of these agents can be fully determined. In the meantime, intramuscular aripiprazole, with its favourable tolerability profile, is a valuable treatment option for agitation in patients with schizophrenia, schizoaffective disorder, schizophreniform disorder or bipolar I disorder.