To better identify individuals on chronic opioid therapy (COT) at high risk for aberrant-drug related behavior (ADRB). We examine whether patients with low level alcohol and drug use have similar characteristics to those with alcohol and drug disorders. We then examined the relationship of alcohol and drug use to ADRBs among COT patients. The sample was 972 randomly selected COT patients (age 21-80 years old) from a large health system in Northern California, USA, and interviewed in 2009. Logistic regression models were used to model the dependent variables of: alcohol use, illicit drug use, alcohol disorders, illicit drug disorders, and ADRBs. The odds of daily/weekly alcohol use were lower for those with a high daily opioid dose (120+ mg/day vs. <20 mg/day) (OR = 0.32, p < 0.010). Illicit drug disorders were associated with depression (OR = 2.31, p < .001) and being on a high daily opioid dose (OR = 5.51, p < .01). Participants with illicit drug use had higher odds of giving (OR = 2.57, p < 0.01) and receiving opioids from friends or family (OR = 3.25, p < 0.001), but disorder diagnoses were not associated with ADRBs. Findings reinforce that illicit drug use should be of high concern to clinicians prescribing opioids, and suggest it should be considered separately from alcohol use and alcohol disorders in the evaluation of ADRBs. Frequent alcohol use is low, but not uncommon, and suggests a need to discuss specific issues regarding safe use of opioids among persons who use alcohol that may differ from their risk of drug use.