The main advantage of depot antipsychotic medication is that it overcomes the problem of covert noncompliance. Patients receiving depot treatment who refuse their injection or fail to receive it for any other reason can be immediately identified and appropriate action taken. In the context of a carefully monitored management programme, depot treatment can have a major impact on compliance and, consequently, the risk of relapse and hospitalisation can be reduced. Another major advantage is that the considerable individual variation in bioavailability and metabolism with oral antipsychotic drugs is markedly reduced with depot treatment. A better correlation between the dose administered and the concentration of medication found in blood or plasma is achieved with depot treatment, and thus, the clinician has greater control over the amount of drug being delivered to the site of activity. A further benefit of depot treatment is the achievement of stable plasma concentrations over long periods, allowing injections to be given every few weeks. However, this also represents a potential disadvantage in that there is a lack of flexibility of administration. Should adverse effects develop, the drug cannot be rapidly withdrawn. Furthermore, adjustment to the optimal dose becomes a long term strategy. The controlled studies of low dose maintenance therapy with depot treatment suggest that it can take months or years for the consequences of dose reduction, in terms of increased risk of relapse, to become manifest. When weighing up the risks and benefits of long term antipsychotic treatment for the individual patient with schizophrenia, the clinician must take into account the nature, severity and frequency of past relapses, and the degree of distress and disability related to any adverse effects. However, the clinical decision to prescribe either a depot or an oral antipsychotic for maintenance treatment will probably rest largely on an assessment of the risk of poor compliance in the particular patient. There is no convincing evidence that the range, nature or severity of adverse effects reported with depot treatment is significantly different from that seen with oral treatment, and depot treatment has been shown to be as good or better than oral medication in preventing or postponing relapse. Furthermore, when adjusting the dose or frequency of depot injection, to improve control of psychotic symptoms or reduce adverse effects, the clinician can be confident that the dose prescribed is the dose being received by the patient.