A total of 98 consecutively admitted psychiatric inpatients were asked for their daily consumption of coffee, tea and other products containing caffeine. Calculation of the corresponding daily caffeine intake was performed using data from the literature and from caffeine measurements carried out in different coffee and tea preparations in the hospital. Of the patients 13% presented a high (> or = 750 mg daily) caffeine consumption before hospitalization. The average caffeine consumption per day decreased from 405 mg before to 332 mg during hospitalization (P < 0.04), but the before and during hospitalization caffeine consumptions were highly correlated (rho = 0.651; P < 0.00001). The decrease in caffeine consumption seems to be influenced by a lower availability of caffeine at hospital. Among the diagnostic groups (DSM-III-R criteria), the caffeine intake was highest in schizophrenia and lowest in anxiety and major depression patients. Patients under a neuroleptic treatment before admission presented a higher caffeine intake. At hospital the high caffeine users showed the highest score on the factor depression (Hopkins Symptom Checklist; HSCL-58). However, the influence of other factors, such as weight and cigarette consumption, which correlated also with the caffeine intake (rho = 0.359; P < 0.001; and rho = 0.83; P < 0.00001, respectively), have also to be considered. Our data suggest that inquiry into caffeine consumption should be included routinely for psychiatric patients, e.g. at admission, because patients with a psychotic disorder undergo a higher risk for an excessive caffeine consumption.