The history, rationale, and development of the Structured Clinical Interview for DSM-III-R (SCID) is described. The SCID is a semistructured interview for making the major Axis I DSM-III-R diagnoses. It is administered by a clinician and includes an introductory overview followed by nine modules, seven of which represent the major axis I diagnostic classes. Because of its modular construction, it can be adapted for use in studies in which particular diagnoses are not of interest. Using a decision tree approach, the SCID guides the clinician in testing diagnostic hypotheses as the interview is conducted. The output of the SCID is a record of the presence or absence of each of the disorders being considered, for current episode (past month) and for lifetime occurrence.