The authors compared the diagnoses made for 50 patients in an emergency room with those made during a subsequent inpatient hospitalization. They found an acceptable level of reliability for broad diagnostic categories, such as psychosis, depression, and alcoholism. The authors believe such diagnostic reliability is sufficient for emergency assessment and triage. However, the diagnosis of more specific subtypes of mental illness, such as schizophrenia and bipolar disorder, were not made reliably in the emergency room. The authors point out the risk of diagnostic labeling, and suggest that the tendency to overlook nonalcoholic substance abuse deserves special attention.