Achalasia is a motility disorder of the esophagus characterized by total loss of esophageal peristalsis and by defective lower esophageal sphincter function. The etiology of achalasia is poorly understood. Achalasia occurs across the lifespan, but is uncommon in children. Most patients have progressive dysphagia for both liquids and solids. This article describes the symptoms of achalasia, its diagnosis, and treatment. The emphasis is on primary achalasia. Case studies illustrate common findings in patients with achalasia. The importance of patient education for effective management of this chronic illness is discussed.