In follow-up of 1,500 drug-using applicants to the NIMH civil commitment program under Titles I and III of the Narcotic Addict Rehabilitation Act, efforts were made to measure the reliability and validity of self-reported criminal and drug-taking behavior. Various methods to assure reliable and valid responses were developed and implemented. These methods included choice of interviewer, intraquestionnaire safeguards, interview-reinterview procedures, and use of police records and urinalysis reports. Overall, the results indicated that the responses for 829 respondents were reliable. The greatest limitation to the validity study was the incomplete and unreliable police records and urinalysis reports.