We present a treatment-based classification approach to the conservative management of low back syndrome. The approach has three levels of classification based on historical information, behavior of symptoms, and clinical signs. We first distinguish patients whose conservative care can be managed predominantly and independently by physical therapists versus patients who require consultation with other services (eg, psychology) or who require referral because of possible serious nonmusculoskeletal pathology. Once patients who can be managed by physical therapists are identified, the next level of classification is to stage their condition with regard to severity. We propose three stages: stage I for patients in the acute phase where the therapeutic goal is symptom relief, stage II for patients in a subacute phase where symptom relief and quick return to normal function are encouraged, and stage III for selected patients who must return to activities requiring high physical demands and who demonstrate a lack of physical conditioning necessary to perform the desired activities safely. The remainder of the article focuses on a third level of classification for stage I only in which patients are classified into distinct categories that are treatment-based and that specifically guide conservative management. The entire approach is diagnosis based, with specific algorithms and decision rules as well as examples presented.