Objectives: The purpose of this study was to compare knowledge in managing patients with low back pain (LBP) between physical therapists and family practice physicians. Methods: Seventy-three physical therapists and 30 family practice physicians completed standardized examinations assessing knowledge, attitudes, the usefulness of clinical practice guidelines, and management strategies for patients with LBP. Beliefs of physical therapists and family practice physicians about LBP were compared using relative risks and independent t-tests. Results: Scores related to knowledge, attitudes, and the usefulness of clinical practice guidelines were generally similar between the groups. In addition, there was no difference between the groups for knowledge regarding optimal management strategies for patients with LBP. However, physical therapists were less likely to have difficulty assessing motivation levels of patients with LBP compared to family practice physicians (64.6% vs 26.7%; relative risk: 2.41 [95% confidence interval: 1.30-4.48] and physical therapists were less likely to agree that interventions by health care providers have little positive effect on the natural history of acute LBP (17.8% vs. 50.0%; relative risk: 0.36 [95% confidence interval: 0.19-0.66]). Discussion: The results of this study may have implications for third-party payers and health care administrators regarding the utilization of physical therapists in the management of patients with LBP in expanded scopes of practice, including direct access and potential placement in primary care clinics.