Tobacco smoking and chronic pain are highly comorbid conditions. Smoking and pain have been proposed to influence each other through a reciprocal positive feedback loop, in which pain increases motivation to smoke and smoking worsens pain over time. Nicotine has been shown to provide mild, short-term anti-nociceptive effects, which may contribute to powerful negative reinforcement learning. Conversely, smoking withdrawal exacerbates pain, presenting a potential barrier to smoking cessation. The goal of the proposed research is to examine whether switching to Very Low Nicotine Content (VLNC) cigarettes can directly weaken the pain-smoking reinforcement cycle, and attenuate withdrawal-induced hyperalgesia, among smokers with chronic pain. The research will employ a randomized between-subjects design to evaluate the effects of smoking VLNC’s versus Normal Nicotine Content (NNC) cigarettes on smoking behavior, pain, withdrawal symptoms and motivation to quit among daily smokers with chronic (>3 months) non-cancer back pain. Moreover, ecological momentary assessments (EMA) will be used to examine changes in bidirectional associations between pain, smoking urge and behavior as a function of cigarette condition. Participants will complete 1-week of baseline EMA while smoking their usual brand of cigarettes to familiarize them with study procedures; they will then be randomized to 4-weeks of NNCs or VLNCs. EMA will continue during weeks 1 and 4 of study cigarette use, and will assess smoking behavior and urge, negative affect, and pain intensity and interference. Participants will attend weekly in-person visits to obtain biomarker verification of cigarette compliance, and will complete measures of nicotine dependence, self-efficacy and motivation to quit, and pain-related coping. At the start of the study and at the end of 4-weeks of study cigarette use, a 24-hr smoking abstinence test will be used to assess withdrawal symptoms and withdrawal-induced hyperalgesia. In general, we hypothesize that switching to VLNCs will attenuate the bidirectional associations between smoking and pain as assessed via EMA, and will lead to decreased symptoms of withdrawal and pain during the 24-hour abstinence test. We also hypothesize that VLNCs will be associated with improvements in abstinence self-efficacy and intention to quit smoking, and decreased reliance on smoking to cope with pain. These results will provide critical insights into the role of nicotine in maintaining smoking/pain associations and the potential for VLNCs to extinguish learned associations to promote smoking cessation in this vulnerable population.