The Achilles tendon, the largest tendon in the body, is vulnerable to injury because of its limited blood supply and the combination of forces to which it is subjected. Aging and increased activity (particularly velocity sports) increase the chance of injury to the Achilles tendon. Although conditions of the Achilles tendon are occurring with increasing frequency because the aging U.S. population is remaining active, the diagnosis is missed in about one fourth of cases. Injury onset can be gradual or sudden, and the course of healing is often lengthy. A thorough history and specific physical examination are essential to make the appropriate diagnosis and facilitate a specific treatment plan. The mainstay of treatment for tendonitis, peritendonitis, tendinosis, and retrocalcaneobursitis is ice, rest, and nonsteroidal anti-inflammatory drugs, but physical therapy, orthoties, and surgery may be necessary in recalcitrant cases. In patients with tendon rupture, casting or surgery is required. Appropriate treatment often leads to full recovery.