RATIONALE: Among opioid-treated chronic pain patients, response inhibition deficits in emotional contexts may contribute to opioid misuse. OBJECTIVES: Using high-frequency heart rate variability (HF-HRV) to index-impaired response inhibition, we examined associations between opioid misuse and response inhibition in emotional and neutral contexts in a sample of opioid-treated chronic pain patients. METHOD: Chronic pain patients taking opioid analgesics (N = 97) for >/= 90 days completed an Emotional Go/NoGo task that presented an inhibitory control challenge in the context of neutral, opioid, negative affective, and positive affective background images while HF-HRV was computed. Opioid misuse and craving were assessed. Using a validated cut-point on the Current Opioid Misuse Measure, participants were classified as opioid misusers or non-misusers. Opioid misuse was examined as a predictor of behavioral and HF-HRV metrics of response inhibition. RESULTS: Negative affective and opioid images elicited more errors of commission (p = .002, eta(2)(partial) = .16) and slowed reaction times (p = .045, eta(2)(partial) = .09) compared to neutral and positive affective images, respectively. Though no between-group behavioral differences were observed on the task, opioid misusers exhibited significantly blunted phasic HF-HRV during the task relative to non-misusers (p = .027, eta(2)(partial) = .11). HF-HRV during the task was significantly inversely associated with opioid craving. It was not clear whether these autonomic findings reflected a durable phenotypic difference between groups or between-group differences in opioid dosing and withdrawal. CONCLUSION: Reduced parasympathetic regulation during inhibitory control challenge may indicate heightened opioid misuse risk among opioid-treated chronic pain patients.