鈥� A psychiatric diagnostic interview that can be reliably and validly administered by nonpsychiatric physicians and lay interviewers has both research and clinical applications. We examined the interrater reliability and procedural validity of the Renard Diagnostic Interview (RDI), an instrument designed for these purposes. Randomly selected psychiatric inpatients were interviewed once by a psychiatrist using our standard departmental research interview and were then given RDIs by two psychiatrists, two lay interviewers, or one of each. The reliability of the RDI is estimated by examining diagnostic concordance for the two RDI interviews. Procedural validity is estimated by examining diagnostic concordance between the RDI and the traditional departmental interview. Both reliability and procedural validity were found to be high, and the study demonstrates that lay interviewers using the RDI after a brief period of training can obtain accurate diagnostic information.