To describe the National Institute of Mental Health Diagnostic Interview Schedule for Children Version IV (NIMH DISC-IV) and how it differs from earlier versions of the interview. The NIMH DISC-IV is a highly structured diagnostic interview, designed to assess more than 30 psychiatric disorders occurring in children and adolescents, and can be administered by "lay" interviewers after a minimal training period. The interview is available in both English and Spanish versions. An editorial board was established in 1992 to guide DISC development and ensure that a standard version of the instrument is maintained. Preliminary reliability and acceptability results of the NIMH DISC-IV in a clinical sample of 84 parents and 82 children (aged 9-17 years) drawn from outpatient child and adolescent psychiatric clinics at 3 sites are presented. Results of the previous version in a community sample are reviewed. Despite its greater length and complexity, the NIMH DISC-IV compares favorably with earlier versions. Alternative versions of the interview are in development (the Present State DISC, the Teacher DISC, the Quick DISC, the Voice DISC). The NIMH DISC is an acceptable, inexpensive, and convenient instrument for ascertaining a comprehensive range of child and adolescent diagnoses.