To evaluate the validity of 2 self-report methods for estimating cocaine us
e, Timeline Follow-Back (TLFB) and weekly calendar reports from 65 patients
with a cocaine use disorder were compared with urine drug test results. Th
e TLFB showed fair to moderate validity, and the weekly calendar showed mod
erate to high validity in measuring the frequency of cocaine use. Similar r
esults were obtained when the self-report measures were used to time specif
ic cocaine use episodes. In addition to evidence for superiority of the wee
kly calendar, the validity of self-reports was inversely related to the per
centage of positive urine test results. Furthermore, there was some evidenc
e that validity increased as the time window over which the comparisons wer
e drawn increased. Given the central role of self-reports in the clinical a
nd research evaluation of drug use, factors affecting their validity warran
t further investigation.