Selective serotonin re-uptake inhibitors are widely used for the treatment of depression suffered by adults with learning disabilities. However, the presentation, time of onset and prevalence of treatment emergent symptoms, have not been extensively studied in adults with learning disabilities. The aim of this study was to determine these aspects of treatment. The study design involved retrospective analysis of case notes of all adults with learning disabilities treated with either fluoxetine or paroxetine for depression. During 31% of treatment episodes, patients suffered treatment emergent symptoms during treatment with either selective serotonin re-uptake inhibitor (SSRI). These symptoms subsided on discontinuation of the SSRI. The common emergent symptoms in this group were elevated mood (39%), decreased sleep (35%), hyperactivity (30%), overtalkativeness (26%), agitation (24%) and aggression (37%). In 20% symptoms developed within 1 month and in 67% within 7 months of starting treatment with a SSRI. There were no significant differences noted in the frequency and nature of treatment emergent symptoms between fluoxetine and paroxetine. Few guidelines, if any, exist for initiating and continuing antidepressant treatment for therapeutic or prophylactic use in this patient population. Close monitoring of efficacy and tolerability, including treatment emergent psychiatric symptoms is warranted. Copyright 2001 John Wiley & Sons, Ltd.