This randomized clinical trial evaluated the efficacy of injections of a dextrose-glycerine-phenol connective tissue proliferant into the posterior ligaments, fascia, and joint capsules to treat chronic low back pain. Seventy-nine patients with chronic low back pain that had failed to respond to previous conservative care were randomly assigned to receive a double-blind series of six injections at weekly intervals of either Xylocaine/saline solution or Xylocaine/proliferant into the posterior sacroiliac and interspinous ligaments, fascia, and joint capsules of the low back from L4 to the sacrum. Patients were observed with a visual analog, disability, and pain grid scores, and with objective computerized triaxial tests of lumbar function for 6 months following conclusion of injections. Pretreatment imaging tests with either magnetic resonance imaging (MRI) or computed tomography (CT) scans were performed in all patients. Thirty of the 39 patients randomly assigned to the proliferant group achieved a 50% or greater diminution in pain or disability scores at 6 months compared to 21 of 40 in the group receiving lidocaine (p = 0.042). Subjective parameters measured at 6 months posttreatment improved (p < 0.001) overall in both the treatment and control group compared to baseline. Improvements in visual analog (p = 0.056), disability (p = 0.068), and pain grid scores (p = 0.025) were greater in the proliferant group. Objective testing of range of motion, isometric strength, and velocity of movement showed significant improvements in both groups following treatment but did not favor either group. The MRI and CT scans showed significant abnormalities in both groups, but these did not correlate with subjective complaints and were not predictive of response to treatment.