Acute low back pain is one of the most common reasons for adults to see a family physician. Although most patients recover quickly with minimal treatment, proper evaluation is imperative to identify rare cases of serious underlying pathology. Certain red flags should prompt aggressive treatment or referral to a spine specialist, whereas others are less concerning. Serious red flags include significant trauma related to age (i.e., injury related to a fall from a height or motor vehicle crash in a young patient, or from a minor fall or heavy lifting in a patient with osteoporosis or possible osteoporosis), major or progressive motor or sensory deficit, new-onset bowel or bladder incontinence or urinary retention, loss of anal sphincter tone, saddle anesthesia, history of cancer metastatic to bone, and suspected spinal infection. Without clinical signs of serious pathology, diagnostic imaging and laboratory testing often are not required. Although there are numerous treatments for nonspecific acute low back pain, most have little evidence of benefit. Patient education and medications such as nonsteroidal anti-inflammatory drugs, acetaminophen, and muscle relaxants are beneficial. Bed rest should be avoided if possible. Exercises directed by a physical therapist, such as the McKenzie method and spine stabilization exercises, may decrease recurrent pain and need for health care services. Spinal manipulation and chiropractic techniques are no more effective than established medical treatments, and adding them to established treatments does not improve outcomes. No substantial benefit has been shown with oral steroids, acupuncture, massage, traction, lumbar supports, or regular exercise programs.