Back pain is an important problem for primary care physicians; it is common, costly, and controversial. Back pain is the second leading symptom prompting all physician visits in the United States. There are wide geographic variations in medical care for this problem, and surgical rates in the United States are twice those of most developed countries. The treatment of back pain has followed a series of fads and fashions, and work disability resulting from back pain continues to rise. For all these reasons, primary care clinicians have an important role in improving the care of patients with low back pain. Primary care clinicians face unique problems in treating these patients. First, in primary care, most patients have uncomplicated low back pain, and identifying the rare patient with an underlying malignancy or neurologic deficit is like looking for a needle in a haystack. Second, these practitioners face two populations with nonspecific back pain: one that is likely to improve no matter what (who mostly need reassurance), and a smaller group (about 20%) who are prone to development of chronic back pain and who present complex psychosocial and occupational problems. Third, these problems must be dealt with in the typical setting of a 15-minute patient visit. Finally, lifestyle changes in exercise, weight loss, and smoking cessation may be major parts of patient treatment, and improving compliance with such interventions always is a major challenge. Primary care investigators studying back pain face at least three important challenges. One is to identify more efficient diagnostic strategies that will alleviate doctors' and patients' anxieties. Second is to develop a better theory to explain the large majority of episodes of nonspecific low back pain. At present, competing theories generate competing and conflicting treatments, generating frustration among patients and loss of credibility for clinicians. Third, we need better science, with greater methodologic rigor in the evaluation of the many nonsurgical treatments used for back pain in the primary care setting.