OBJECTIVE Description of use of medication by people with mental handicaps in relation to age, level of mental handicap and living facility. METHODS Cross-sectional study. METHODS Institutions and group homes for people with mental handicaps in North Brabant and Limburg, the Netherlands. METHODS Of a patient sample (n = 1265), stratified according to age and living facility (i.e. institution or group home) data were collected by means of questionnaires to be completed by the general practitioners. For 101 persons data about level of mental handicap were lacking. RESULTS 57% of the patients used one or more drugs. The numbers of drugs used were significantly related to (increased) age and level of mental handicap. Older patients more often used antipsychotics, laxatives and cardiovascular medication, younger ones more often used anticonvulsants. More severely handicapped persons used antipsychotics, anticonvulsants, laxatives, antacids, psychoactive medication and gastrointestinal medication more often. There was no relationship between amount of medication and living facility. CONCLUSIONS Many mentally handicapped use medication. Since epilepsy, psychiatric and behavioural diseases and gastrointestinal problems are frequent, and because the patients offer little spontaneous information, alertness with respect to drug interaction and side effects is indicated.