Background: A comprehensive systematic review was performed to establish the current evidence base regarding the effectiveness of antidepressant medication for the management of behaviour problems in adults with intellectual disabilities. Method: An electronic search of PsycInfo, Embase, Medline and Cinahl databases was conducted spanning the time period 1990 to October 2005 for primary trials. This was supplemented by hand searching and cross-referencing of relevant reviews. Strict scientific methodology requirements were formulated that the studies had to meet in order to merit inclusion in this review. Results: One crossover randomized controlled trial in a small cohort, seven prospective uncontrolled trials and two retrospective studies were yielded in the search. Of these, one explored the effectiveness of the tricyclic antidepressant--clomipramine, and nine considered various selective serotonin reuptake inhibitors (SSRIs). Conclusion: Evidence based primarily on a small number of either prospective or retrospective case studies that included a small number of participants and often used non-validated outcome measures for a short period of follow-up, suggests that antidepressants, particularly SSRIs, show improvement of aggression and self-injurious behaviour on average in less than 50% of cases and the rest show either no improvement or deterioration. The effect is most pronounced in the presence of an underlying anxiety or an associated diagnosis of obsessive-compulsive disorder. Most studies have highlighted the concern regarding adverse effects.