Achalasia is defined as the presence of esophageal outflow obstruction due to impaired relaxation of the LES with absent or spastic contractions in the esophageal body in the absence of structural obstruction in the esophageal body or esophagogastric junction (EGJ). The clinical manifestations of achalasia are a consequence of obstruction in esophageal transit owing to abnormal swallow-induced LES relaxation. Incomplete LES relaxation and abnormal esophageal body peristalsis can also be seen in pseudoachalasia, which needs to be distinguished from achalasia. Diagnosis of achalasia requires recognition of presenting symptoms as well as appropriate use and interpretation of diagnostic testing. The treatment of achalasia is palliative, and its main goal is to eliminate the functional obstruction caused by the non-relaxing and often hypertensive LES, thus improving the emptying of the esophagus into the stomach. Treatment modalities are Endoscopic (PD, botulinum toxin injection [BTI] of the LES, POEM) and Surgical (LHM with partial fundoplication). Medications are of very limited value