Recent reviews conclude that there is some evidence that drug abusers' self-reports are reliable and valid. However, there are wide variations among studies depending upon the samples and procedures used to obtain the data. The current study was conducted to extend the findings in this area. An examination of the intake interviews and same day urinalyses on 150 patients enrolling for outpatient opioid detoxification or maintenance revealed a fairly high agreement between drug use self-reports and urinalyses. A second study (N = 70) looking at the validity of self-reported drug use at intake and at 4 weeks follow-up revealed some noticeable changes in validity measures, suggesting that contingencies on positive urine results influence self reported drug use of addicts.