There is considerable evidence linking developmental pathology with serotonergic abnormalities. Individuals with mental retardation may be particularly susceptible to dysfunction in the serotonin system. The development of more selective drugs that modify serotonergic function appears to have provided an important treatment option for a number of target behaviors, especially those associated with anxiety and depression, in persons with intellectual disability. Clinicians treating this population need to be familiar with the pharmacology of these agents, known collectively as the selective serotonin reuptake inhibitors. This article reviews the pharmacokinetics and pharmacodynamics of these compounds, as well as their potential effects on the developing brain.