Problem Statement: Because of the lack of evidence in support of a pathology-based approach to low back pain (LBP), many researchers advocate the use of classification systems that classify patients with LBP based on common clinical characteristics. Treatment based on direction tolerance can improve circulation, diminish pain and inflammation, restore normal motion, and reduce fear-avoidance beliefs. Treatment performed in the standing position can functionally integrate related regions of the body, can replicate normal tissue loading in standing position, replicate normal proprioceptive demands of motion performed in standing position, and address underlying movement impairments in related regions that may contribute to compensatory tissue pathology in the low back. The problem is that none of the existing functional classification systems for evaluation and treatment of LBP are designed for this purpose. The Direction Tolerance System (DTS) is a new functional classification system that is based on direction tolerance and performed entirely in the standing position. Objectives: The purpose of this research was to investigate the reliability, outcome, and prognostic ability of the DTS for evaluation and treatment of LBP. Methods: This exploratory research was a prospective cohort study with 60 patients seeking physical therapy (PT) for treatment of LBP by 5 different therapists. All patients were evaluated and treated for 8 visits using the DTS. Reliability was measured by comparing DTS scores (DTI) on visits 1 and 2. DTS treatment consisted of a scripted flexibility and strengthening exercise program based on motions that were determined to be non-aggravating during the DTS examination. Outcome was assessed using the DTI, modified Oswestry Disability Questionnaire (ODQ), Numeric Pain Rating Scale (NPRS) and Fear-Avoidance Beliefs Questionnaire Physical Activity Subscale (PABQ-PA). Baseline variables were assessed for correlation with successful outcome and ability to predict a successful outcome. Results: (1) Group intra-rater reliability between visits 1 and 2 using ICC (3,1) was good (.80, p<.001); (2) The group success rate was 62%, which exceeded the expected 50% success rate. (3) Baseline variables were not associated with a successful outcome and did not significantly predict a successful outcome. Discussion: The DTS is a simple, reliable and effective method of evaluating and treating LBP, and with proper training, can be used by clinicians.