Abstract
Ninety-eight male patients on methadone maintenance treatment provided weekly urine screens for typical substances of abuse and periodic screens for 9-carboxy-tetrahydrocannabi-nol (THC). Although different in some demographics and personality characteristics, patients who were THC-positive (THC+; n = 54, 55-1 %) were no more likely to use other illicit drugs and showed similar treatment retention, employment, and cognitive function to those who were THC-negative. THC+ patients reported more marijuana use at admission. Marijuana use exhibits no apparent impact on methadone treatment outcome. Routine urine screening for THC in methadone programs is not currently justified.