Official records offer a relatively inexpensive, nonintrusive strategy for checking on the accuracy of self-reported drug use. Responses of a small sample (N = 67) of former drug treatment clients interviewed using procedures exactly modeled on the National Household Survey on Drug Abuse were compared to their clinic records. The accuracy of reports compared to clinic records varied by drug, with the percentage of known users reporting their use highest for marijuana, followed by cocaine and hallucinogens, and lowest for heroin. Almost half of this sample of former treatment clients denied ever receiving drug treatment.