Study Design: Test re-test methodological design using a sample of convenience. Objectives : Examine the effects of a 6-week criterion-based stabilization program on subjects with surgical and non-surgical medical diagnoses of lumbar segmental instability. Dependent variables assessed included Oswentry Low Back Pain Disability Questionnaire and cross sectional area of the lumbar multifidus. Background: Lumbar segmental instability has emerged as a characteristic finding in many phases of spinal pain. Onset of lumbar segmental instability may be insidious in cases of isthmic spondylolisthesis of acute in cases of disc herniation. Surgical treatment of these conditions produces specific atrophy. Lumbar multifidus atrophy persists if specific interventions are not performed. Correlations between cross sectional area of the lumbar multifidis and disability questionnaires have not been demonstrated in these two medical diagnoses. Methods and Measures: All subjects completed the Oswestry Low Back Pain Disability Questionnaire and received real-time ultrasound measurements to their lumbar multifidis at pre and post-test. A convenience sample fo the first 21 subjects participated in the intervention group, while the next 17 subjects participated in the control group. Results: Odds ratios demonstrate a 49:1 chance of improvement with this program. Speaman’s rank correlations revealed no correlation between change in cross sectional area and improvement in self-report questionnaire. Conclusion: This specific stabilization program produces improvements in self-report of disability after six-weeks. During the study timeframe, no measurable change in cross sectional area of the lumbar multifidis was correlated with improvements in Oswestry Low Back Pain Disability Questionnaire scores.