Objectives: To compare selected physical and bio-behavioral improvements following McKenzie intervention in individuals with discogenic chronic low back pain (CLBP) demonstrating centralization and partial centralization of pain. Design: Prospective cohort study with three assessments; at base line and two follow-ups. Setting: Two out-patient orthopedic Physical Therapy clinics. Participants: 105 volunteers with CLBP (52 men and 53women) average ages 41.9 and 37.1 years. Methods: Subjects filled out pain and related fear and disability questionnaires, performed selected physical tests then underwent a McKenzie assessment protocol. McKenzie assessment protocol utilizes directional preference exercises to determine the pain centralization-phenomenon. Subjects were divided into 2-groups; completely centralized group (CCG) and partially centralized group (PCG), and underwent a McKenzie intervention. Outcome measurements were repeated at the end of the 5th and 10th weeks after completing the treatment Outcome Measurements: Pain related fear and disability beliefs were assessed using the Fear Avoidance Belief Questionnaires (FABQ) and Disability Belief Questionnaire (DBQ). The time of sit-to-stand, forward bending, and customary and fast walking was recorded. Pain (anticipated vs. actual perception), were measured before and after each physical task. Descriptive statistics, Chi-square, paired t-tests, repeated measures ANOVA were used for longitudinal comparisons across assessment intervals at p<0.05 level. Results: Significant improvements in patient physical performance times and bio-behavioral variables were observed on the 5th week following the intervention, but tended to regress thereafter. Conclusions: In this cohort study of CLBP both CCG and PCG patients demonstrated significant measurable improvements in physical performances that remained stable for 10 weeks as a result of improved pain and related fear and disability beliefs.