Objective: Although mindfulness meditation (MM) is increasingly used for chronic pain treatment, limited evidence supports its clinical application for opioid-treated chronic low back pain (CLBP). The goal of this study was to determine feasibility, acceptability, and safety of an MM-based intervention in patients with CLBP requiring daily opioid therapy. Design: 26-week pilot randomized controlled trial comparing MM-based intervention, combined with usual care, to usual care alone. Setting: Outpatient. Patients: Adults with CLBP treated with ‡30 mg of morphine-equivalent dose (MED) per day for 3 months or longer. Interventions: Targeted MM-based intervention consisted of eight weekly 2-hour group sessions and home practice (30 minutes/d, 6 days/wk) during the study. ''Usual care'' for opioid-treated CLBP was provided to participants by their regular clinicians. Outcome measures: Feasibility and acceptability of the MM intervention were assessed by adherence to intervention protocol and treatment satisfaction among experimental participants. Safety was evaluated by inquiry about side effects/adverse events and opioid dose among all study participants. Results: Thirty-five participants enrolled during the 10-week recruitment period. The mean age (-standard deviation) was 51.8 -9.7 years; the patients were predominantly female, with substantial CLBP-related pain and disability, and treated with 148.3 -129.2 mg of MED per day. All participants completed baseline assessments; none missed both follow-up assessments or withdrew. Among experimental participants (n = 21), 19 attended 1 or more intervention sessions and 14 attended 4 or more. They reported, on average, 164.0 -122.1 minutes of formal practice per week during the 26-week study and 103.5 -111.5 minutes of brief, informal practice per week. Seventeen patients evaluated the intervention, indicating satisfaction; their qualitative responses described the course as useful for pain management (n = 10) and for improving pain coping skills (n = 8). No serious adverse events or safety concerns occurred among the study participants. Conclusions: MM-based intervention is feasible, acceptable, and safe in opioid-treated CLBP.