Context Patients suffering from chronic low back pain (cLBP) are often unsatisfied with conventional medical care and seek alternative therapies. Many mind-body techniques are said to help patients with low back pain by enhancing body awareness, which includes proprioception deficit in cLBP, but have not been rigorously studied in cLBP. Breath therapy is a western mind-body therapy integrating body awareness, breathing, meditation, and movement. Preliminary data suggest benefits from breath therapy for proprioception and low back pain. Objective To assess the effect of breath therapy on cLBP. Design Randomized, controlled trial. Setting Academic medical center. Participants Thirty-six patients with cLBP. Interventions Six to eight weeks (12 sessions) of breath therapy versus physical therapy. Main outcome measures Pain by visual analog scale (VAS), function by Roland Scale, overall health by Short Form 36 (SF-36) at baseline, six to eight weeks, and six months. Balance as a potential surrogate for proprioception and body-awareness measured at the beginning and end of treatment. Results Pre- to post-intervention, patients in both groups improved in pain (VAS: -2.7 with breath therapy, -2.4 with physical therapy; SF-36: +14.9 with breath therapy and +21.0 with physical therapy). Breath therapy recipients improved in function (Roland: -4.8) and in the physical and emotional role (SF-36: +15.5 and 14.3). Physical therapy recipients improved in vitality (SF-36: +15.0). Average improvements were not different between groups. At six to eight weeks, results showed a trend favoring breath therapy; at six-months, a trend favoring physical therapy. Balance measures showed no improvements and no correlations with other outcomes. Conclusions Patients suffering from cLBP improved significantly with breath therapy. Changes in standard low back pain measures of pain and disability were comparable to those resulting from high-quality, extended physical therapy. Breath therapy was safe. Qualitative data suggested improved coping skills and new insight into the effect of stress on the body as a result of breath therapy. Balance measures did not seem to be valid measures of clinical change in patients' cLBP.