We have conducted a prospective, double blind trial of low level laser therapy (LLLT) in musculoskeletal injuries to assess its efficacy. We assigned patients with a variety of painful skeletal soft tissue conditions to one of two treatment groups, treatment from a functional machine, placebo treatment from an inactive machine. Both machines were identical and both appeared functional. The operative status of each machine was unknown to both the therapist and the patient. The results suggest that LLLT has no significant therapeutic effect and acts primarily as a placebo.