The authors applied modern criteria to the diagnosis of 254 patients admitted to the psychiatric wards of an urban hospital. They found that only 16 (6.3%) met the St. Louis criteria for schizophrenia. Other studies using similar criteria also reported a consistently low prevalence of schizophrenia in general psychiatric inpatient populations. However, 30 "undiagnosed" patients (12%) in this study narrowly missed the definite diagnosis of schizophrenia because of the presence of affective disorder and/or insufficient duration of symptoms. The authors discuss the clinical and research implications of these findings.