As an example of iatrogenic diabetes, we discuss the problem of diabetes mellitus in patients receiving atypical antipsychotics. The risk of diabetes mellitus appears to be different according to various molecules with, by decreasing order, clozapine, olanzapine, risperidone and quetiapine, and finally amisulpride, aripiprazole and ziprasidone. A careful analysis of published case reports and series indicates the existence of two different problems: 1) the rather common development of impaired glucose tolerance or diabetes mellitus (often associated with metabolic syndrome) related to weight gain in individuals at risk for type 2 diabetes; and 2) the occurrence of rare cases of acute metabolic episodes with severe ketoacidosis and/or pancreatitis whose pathophysiological mechanisms remain largely unknown. Generally speaking, the pathophysiology involves both increased insulin resistance and deficient insulin secretion. Cautious metabolic monitoring of patients receiving atypical antipsychotics is recommended, and the selection of the appropriate drug should be influenced by the metabolic profile of the various molecules and the metabolic risk of the patients who should be treated with atypical antipsychotics.