One of the major challenges for general practitioners is to manage individuals with acute low back pain appropriately to reduce the risk of chronicity. A prospective study was designed to assess the actual management of acute low back pain in one primary care setting and to determine whether existing practice patterns conform to published guidelines. Twenty-four family physicians from public primary care centers of the Basque Health Service in Bizkaia, Basque Country (Spain), participated in the study. A total of 105 patients aged 18-65 years presenting with acute low back pain over a 6-month period were included. Immediately after consultation, a research assistant performed a structured clinical interview. The patients' care provided by the general practitioner was compared with the Agency for Health Care Policy and Research (AHCPR) guidelines and guidelines issued by the Royal College of General Practitioners. The diagnostic process showed a low rate of appropriate use of history (27%), physical examination (32%), lumbar radiographs (31%), and referral to specialized care (33%). Although the therapeutic process showed a relatively high rate of appropriateness in earlier mobilization (77%) and educational advice (65%), only 23% of patients were taught about the benign course of back pain. The study revealed that management of acute low back pain in the primary care setting is far from being in conformance with published clinical guidelines.