Forty alcoholic inpatient men were used to evaluate the test-retest reliability and the validity of a new structured diagnostic interview. The Alcohol Research Center (ARC) Intake Interview was constructed from the Schedule of Affective Disorders and Schizophrenia (SADS) parts I and II and from the Diagnostic Interview Schedule family history section by extracting information on diagnoses most likely to be seen in alcoholic patients and by expanding the data set with questions relevant to alcohol and drug use. The test-retest reliability for patients' primary and secondary diagnoses included a kappa of 1.00 for the comparison of interviewers A and B (100% agreement) and of .76 for interviewers A and C. The validity of ARC Intake Interview patient diagnoses as compared to the SADS demonstrated an overall agreement between 91 and 100%. Reliabilities for labeling of families as positive or negative for specific illness in any first-degree relatives revealed a kappa of 1.00; validities on family diagnoses ranged from 77 to 100%, with the ARC Intake Interview identifying more illness in families than the SADS. Although further evaluation of the ARC Intake Interview is needed, this instrument is recommended to investigators attempting to evaluate the clinical course and treatment needs among alcoholics, especially those patients presenting with multiple diagnoses.