The National Household Survey on Drug Abuse (NHSDA) is the nation’s primary data source for information on the scope and dimensions of drug abuse in the United States. To improve data collection, the NHSDA was converted to a computer-assisted interview format in 1999. This paper reports on the research done to guide the conversion. The main focus of the paper is on the large (n=1,982) field experiment that examined different audio computer-assisted self-interviewing (ACASI) procedures in the fourth quarter of 1997. This field experiment showed that ACASI is likely to increase reporting of drug use among youth; that respondents can, on their own, correct inconsistencies in responses that are detected by the computer, and that ACASI eases the response task for poor readers and less well educated respondents. Tables, notes, references