BACKGROUND:It is unclear whether substance use disorder (SUD) treatment is offered to, or utilized by, patients who are discontinued from long-term opioid therapy (LTOT) following aberrant urine drug tests (UDTs). OBJECTIVE: To describe the proportion of patients who were referred to, and engaged in, SUD treatment following LTOT discontinuation and to examine differences in SUD treatment referral and engagement based on the substances that led to discontinuation. DESIGN: From a sample of 600 patients selected from a national cohort of Veterans Health Administration patients who were discontinued from LTOT, we used manual chart review to identify 169 patients who were discontinued because of a UDT that was positive for alcohol, cannabis, or other illicit or non-prescribed controlled substances. MAIN MEASURES: We extracted sociodemographic, clinical, and health care utilization data from patients' electronic medical records. KEY RESULTS: Forty-three percent of patients (n = 73) received an SUD treatment referral following LTOT discontinuation and 20% (n = 34) engaged in a new episode of SUD treatment in the year following discontinuation. Logistic regression models controlling for sociodemographic and clinical variables demonstrated that patients who tested positive for cannabis were less likely than patients who tested positive for non-cannabis substances to receive referrals for SUD treatment (aOR = 0.44, 95% CI = 0.23-0.84, p = 0.01) or engage in SUD treatment (aOR = 0.42, 95% CI = 0.19-0.94, p = 0.04). Conversely, those who tested positive for cocaine were more likely to receive an SUD treatment referral (aOR = 3.32, 95% CI = 1.57-7.06, p = 0.002) and engage in SUD treatment (aOR = 2.44, 95% CI = 1.00-5.96, p = 0.05) compared to those who did not have a cocaine-positive UDT. CONCLUSIONS: There may be substance-specific differences in clinician referrals to, and patient engagement in, SUD treatment. This suggests a need for more standardized implementation of clinical guidelines that recommend SUD care, when appropriate, following LTOT discontinuation.KEY WORDS: long-term opioid therapy; chronic pain; substance use treatment; physician referral.