In a double-blind, randomized, placebo-controlled study, administration of botulinum toxin A (Botox; Allergan Inc., Irvine, CA) into paraspinal muscles using a novel technique produced significant pain relief in 60% of patients with chronic, refractory low back pain. A similar yield of 53% was noted in a prospective, randomized, open-label study of 75 patients, with 14 months of follow-up. In this study, an early response predicted later responsiveness, with 91% of the responders continuing to respond to repeat injections. The technique of treatment for both studies included covering the whole length of the lumbar erector spinae with one injection given at each lumbar level regardless of pain, tenderness, or trigger point location(s). The dose per injection site was 50 U (Botox), with the total dose per session not to exceed 500 U. Side effects were uncommon and consisted of a transient, mild flu-like reaction in 5% of the patients. Botulinum treatment of paraspinal muscles can reduce pain in a substantial number of patients with refractory chronic low back pain and is safe in the recommended doses.