Acute low back pain will affect more than 80% of the population, with more than 28% of the industrial workforce suffering from lost work. Acute low back pain is recognized as the third most common illness presenting to private practice groups. The psychosocial overtones of depression and anxiety that often coexist or predate the episode of acute low back pain add to its complexity and cost. Diagnosis and treatment options are reviewed based on the Agency for Health Care Policy and Research recommendations of 1994. This article reviews details of the history and physical with emphasis on the importance of a thorough neurologic and psychologic evaluation. "Red flags" that should warn the clinician of the presence of a more acute illness are discussed with recommendations for referral. The treatment of acute low back pain now centers on increasing mobility and functional use of the spine as soon as possible. Nonsteroidal anti-inflammatory agents as well as aspirin and acetaminophen are recommended as first-line drug treatments; they have been found to be equally as effective as muscle relaxants and opioids for the control of pain without the burden of dependence and potential for abuse.