What is known and objective: Current evidence-based guidelines for the treatment of acute low back pain (ALBP) recommend the use of opioid medications only after failure of nonpharmacological therapy, non-steroidal anti-inflammatory drugs and skeletal muscle relaxants and after thorough evaluation of risks and benefits. Despite this recommendation and the state of the opioid epidemic in the United States (US), opioids remain a common drug of choice for ALBP in the emergency department (ED). The purpose of this study was to quantify the prevalence and identify predictors of opioid prescribing for acute lower back pain (ALBP) in emergency departments (EDs) in the United States.Methods: This was a national, cross-sectional study of the National Hospital Ambulatory Care Survey from 2013-2016. ED visits for patients aged ≥18 years treated for ALBP were included. Patients presenting with specified reasons that an opioid may be indicated were excluded. The primary endpoint was frequency of opioids prescribed. A multivariate logistic regression model identified patient-and provider-level predictors of opioid use. Results and discussion:This analysis included 2260 visits for ALBP. Opioids were prescribed in 32.3% of visits. Positive predictors of opioid prescribing were pain score of 7-10 (OR 1.85; 95% CI 1.26-2.70), and patients seen in the Southern (OR 2.53; 95% CI 1.47-4.36) or Western US (OR 2.10; 95% CI 1.19-3.70). Opioids were prescribed less often to patients who received a NSAID or acetaminophen (OR 0.38; 95% CI 0.28-0.52 and OR 0.03; 95% CI 0.01-0.10, respectively). What is new and conclusion:Opioid prescribing rates for ALBP remain high and the predictors identified demonstrate that this prescribing pattern is not uniformly distributed across the patient and provider characteristics studied. K E Y W O R D S low back pain, opioid, opioid prescribing, pain | 699 WALKERLY Et AL. Received an NSAID a 0.36 0.25-0.51 Received acetaminophen a 0.03 0.01-0.10 History of alcohol use disorder 0.51 0.19-1.35a Indicates a statistically significant predictor of receiving an opioid via the logistic regression model.