summary  The Netherlands Pharmacovigilance Centre Lareb has received reports of cases in which risperidone has affected the glucose metabolism. The Dutch Summary of Product Characteristics of Risperdal ® does not refer to this effect. This article describes the cases concerned and reports on comparable cases in the literature and in the WHO database. Since the effects reported for risperidone are similar to the effects of olanzapine and clozapine, it is assumed that the pharmacological mechanisms of all three drugs are associated.