Aims: In an exploratory research of the prevalence of hyperglycaemia or Diabetes Mellitus, type 2, among chronic schizophrenic patients in a chronic ward of a general psychiatric hospital, all patients with the diagnosis of schizophrenia or schizoaffective disorders were asked to cooperate in the study. Methods: Hyperglycaemia or DM, type 2, in the non-fasting patients was diagnosed in accordance with the NHG-guidelines (1999). 93 out of the 99 schizophrenic or schizoaffective patients actually participated in the research. Results: Hyperglycaemia was diagnosed in 11 of the 93 patients, of which only 1 was previously known. The prevalence of hyperglycaemia at the age of 20-49 years was significantly higher than in the general population (15,2% vs 5,7%, OR = 2.959. CI = 1.230-7.119, p < 0.05). The general prevalence of DM, type 2, was significantly raised in comparison to the general population (7,5% vs 1,9%, OR = 4.288, CI = 1.979-9.289, p < 0.001). In spite of a significantly raised prevalence of obesitas in the study population (20% vs 8%, OR = 2.953. CI = 1.698. p < 0.001). no relation with the raised prevalence of hyperglycaemia or DM, type 2, was found, neither was a relation found between diabetic disturbance and the prescribed antipsychotic medication. Conclusions: In an exploratory study of 93 chronic schizophrenic inpatients a significantly raised prevalence of hyperglycaemia and diabetes mellitus type 2 was found, which could not be explained by the raised prevalence of overweight. In contrast to case reports and some recent studies, no relation was found between diabetic disturbance and the prescribed antipsychotic medication. Whether this contrast results from differences in study population or other methodological differences, is a question for further research. This study has three major limitations. One is that the impact of inactivity, one well-known risk factor of diabetes mellitus type 2, was not assessed. The second limitation is the selection of the study population: only chronic, schizophrenic impatients were included in this study. The thrid limitation is the difficulty in assessing the effect of chronic, often decade-long antipsychotic regime of different antipsychotic medication in different dosages on glucose homeostasis. Further research are needed to help to elucidate these questions.