Mental retardation itself is no psychiatric disorder and cannot be treated pharmacologically, whereas some of the associated psychiatric relevant symptoms and disorders respond to medication. Prevalence of psychiatric disorders in mentally handicapped people is 4-5 times higher than in the average population. Therefore, psychopharmacological medication is frequent during inpatient treatment, about 12 to 40%. The spectrum of psychiatric disorders in mentally handicapped individuals resembles the spectrum prevalent in the average population. However, specific aspects are to be considered in pharmacological treatment of mentally handicapped patients: difficulties in differential diagnosis, high rate of comorbidities, multiple medication, special effects and side effects of substances and problems of compliance.