Outcomes of opioid therapy for noncancer pain remain to be more fully explored. Loss of work is among these outcomes. Especially when work loss becomes "chronic" (persists >or=90 days), it has profound psycho-social repercussions that compound suffering of those already in pain. Furthermore, costs escalate as work loss persists. We thus explored associations between opioid therapy for back pain and chronic work loss. Data consisted of workers compensation claims for nonspecific low back pain. We used multivariate analyses to control for diverse covariates. Workers with no opioid prescriptions constituted the reference group. Findings included the following: compared with the (no opioid) reference group, odds of chronic work loss were six times greater for claimants with schedule II ("strong") opioids; compared with the reference group, odds of chronic work loss were 11-14 times greater for claimants with opioid prescriptions of any type during a period of >or=90 days; and three years after injury, costs of claimants with schedule II opioids averaged $19,453 higher than costs of claimants in the reference group. Our analysis was not designed to ascertain antecedent causes, or why chronic work loss occurred in the first place. Rather, we focused on an ensuing consequence of opioid therapy, i.e., the outcome of chronic work loss, which occurred far removed in time (>or=90 days) after the worker's recorded date of back injury. The strong associations observed suggest that for most workers opioid therapy did not arrest the cycle of work loss and pain.