Background: Psychopharmacological intervention in the management of behaviour problems in adults with intellectual disabilities (ID) has become a common treatment strategy. This has become a cause for concern, given that the evidence for its effectiveness is uncertain and most drugs are not licensed for this use. Methods: A comprehensive systematic review of empirical research on the effectiveness of antipsychotic medication was conducted. Electronic and manual searches of literature were conducted. Stringent scientific methodology determined those primary trials that were worthy of inclusion. Results: This review revealed one randomized controlled trial (RCT), one controlled, four uncontrolled prospective and three retrospective case series studies in adults. Additionally, two studies in both adults and children--one crossover RCT and one prospective controlled trial--were found. Conclusion: Presently, there is RCT-based evidence for risperidone to be effective in both adults and children; however, this treatment carries a certain amount of risk associated with adverse effects. There is also evidence to support the use of other antipsychotics, primarily atypicals, but the evidence is based on noncontrolled case studies. There is currently not enough evidence available to recommend specific medication for specific behaviour problems. Before prescribing medication, clinicians should carry out a thorough assessment of behaviour, including its causes and consequences, and draw up a formulation providing the rationale for the prescribed intervention after considering all medication- and nonmedication-based management options.