Chronic low back pain (CLBP) is a common and debilitating problem in older adults. Little exists in the literature about primary care physicians' (PCPs') knowledge of and confidence in managing this problem. A self-administered survey was mailed to PCPs in western Pennsylvania to measure knowledge of the evaluation and treatment of common contributors to CLBP in older adults, confidence in diagnosing these contributors through physical examination, and the association between confidence levels and knowledge. The survey combined items with an ordinal scale on which PCPs ranked their confidence in detecting various contributors to CLBP (e.g., fibromyalgia) using physical examination and patient vignettes followed by multiple choice questions designed to assess knowledge. One hundred fifty-three of 634 surveys were returned (24.1%). Overall, the majority of PCPs did not feel "very confident" in their ability to diagnose any of the contributors of CLBP listed (most items <40%). PCPs felt most confident in detecting scoliosis and least confident detecting myofascial pain of the piriformis muscle. There was a wide range in the number of respondents answering all questions related to a particular topic correctly (3.9% for sacroiliac joint syndrome to 70.4% for hip osteoarthritis). There was no relationship between knowledge scores and confidence ratings (P > .05 for all comparisons). The results point to a need for more PCP education about CLBP in older adults. It also suggests that accurate needs assessment should not rely on physician confidence ratings alone.