Achalasia is a rare motility disorder of the esophagus presenting with symptoms of dysphagia, regurgitation of undigested food, respiratory symptoms (nocturnal cough, recurrent aspiration, pneumonia), chest pain, and weight loss. This chapter focuses solely on idiopathic achalasia. The diagnosis of achalasia should be suspected in any patient complaining of dysphagia for solids and liquids with regurgitation of undigested food and saliva. The first diagnostic step is to rule out anatomical lesions using endoscopic evaluation. Accepting that the loss of neurons (type I and II) or imbalance in nitrergic and cholinergic innervation (type III) is immune-mediated, the ideal treatment should aim to stop this process. Achalasia is a chronic disorder that slowly progresses with time, and thus recurrence of symptoms can be anticipated. Somewhat related is the extent to which we predict recurrence of symptoms.