This study compared structured vs. unstructured interviews for making psychiatric diagnoses. Three clinicians independently diagnosed 56 inpatient-subjects, each using a different method: (1) the unstructured Traditional Diagnostic Assessment (TDA), the standard method of clinical practice; (2) the Structured Clinical Interview for DSM-Clinical Version (SCID-CV), a widely used structured method; and (3) the Computer Assisted Diagnostic Interview (CADI), a structured computer-based method. Once finished, the three clinicians developed a Consensus diagnosis, using Spitzer's LEAD Standard (L=Longitudinal evaluation of symptomatology, E=Evaluation by expert consensus, AD=All Data from multiple sources). Diagnoses were assigned to one of 10 groups (cognitive impairment, general medical condition-induced, alcohol-induced, drug-induced, mania, depression, schizophrenia, schizoaffective, psychosis NOS, and anxiety). Diagnostic accuracy for each method, measured against Consensus, was as follows: TDA-agreement=53.8%, kappa=0.4325 ('fair'); SCID-CV-agreement=85.7%, kappa=0.8189 ('excellent'); CADI -agreement=85.7%, kappa=0.8147 ('excellent'). All three methods reached acceptable levels of diagnostic accuracy. Structured methods (SCID-CV, CADI) were significantly better than the unstructured TDA.