Autism is a disorder characterised by abnormalities in language and social development, and repetitive behaviours. Antipsychotics, including haloperidol and risperidone, are the most widely studied drugs for reducing symptoms in children and adolescents with autism. When administered at relatively low dosages, antipsychotics have been shown to reduce repetitive behaviours (stereotypies) and social withdrawal, as well as a number of related symptoms, such as hyperactivity, aggression, self-abusive behaviour, temper tantrums, lability of mood and irritability. Adverse effects of antipsychotics include sedation, dizziness, increased appetite, weight gain, changes in the electrocardiogram parameters, drooling, hyperprolactinemia and a risk of drug-related dyskinesias. Other agents have been less well studied for the treatment of autism, but there are suggestive data regarding their safety and efficacy. Of these agents, a number have been investigated, based on theories about the aetiology of autism, including SSRIs and naltrexone, although the efficacy of these agents has been limited. Stimulant drugs have been shown to reduce hyperactivity and improve focus, but they may cause behavioural worsening, weight loss and stereotypies de novo. Secretin is a treatment that has received much media attention after reports of efficacy from small open studies, but all controlled studies have failed to show any benefit. In autism, alternative treatments have also been used, but none have shown benefit in well-designed studies.