Achalasia is the best understood and most readily treatable esophageal motility disorder. It serves as a prototype for disorders of the enteric nervous system with degeneration of the myenteric neurons that innervate the lower esophageal sphincter (LES) and esophageal body. Investigations into the pathogenesis have highlighted the importance of nitric oxide and the possible role of an autoimmune response to a viral insult in genetically susceptible individuals. Advances in diagnostic testing have delineated manometric variants of achalasia that have implications for management. Treatment studies have demonstrated the limited efficacy of botulinum toxin as well as less than ideal, long-term effectiveness of both pneumatic dilation and Heller myotomy. This article incorporates these recent developments into the current understanding of achalasia.