The aim of the present study was to determine the prevalence of psychiatric disorders in acutely ill medical inpatients. A total of 313 consecutively admitted patients were interviewed using a semistructured psychiatric interview. Diagnoses were made according to DSM-IV diagnostic criteria during two time periods, the 7 days following admission and the month prior to admission. The results showed that 85 patients (27.2%) received a DSM-IV diagnosis, with several patients having comorbid diagnoses. Major depressive disorder was present in 16 patients (5.1%), most of whom also had major depressive disorder in the month prior to admission. This prevalence rate is above that of the general population (1.2% to 2.8%), but less than that reported in most previous studies (20% to 40%). Forty-three patients (13.7%) had an adjustment disorder, 18 patients (5.8%) had an anxiety disorder, and 17 patients (5.4%) had either alcohol dependence or abuse. Nurses were more proficient than medical staff at identifying patients who had received a DSM-IV diagnosis, recognizing 61% of cases compared with 41% for medical staff.