Achalasia is a serious disorder in which the movement of food and liquids through the esophagus is impaired. It is currently thought to be caused by an inflammatory process that destroys neurons in myenteric ganglia, which affect peristalsis in the esophagus. The factor(s) that precipitate this inflammatory process are unknown; possibilities include environmental agents (such as microbes or toxins) and/or cell-mediated autoimmune reactivity. Recently, infection with a newly described bornavirus has been strongly linked to a disease of exotic birds that displays many striking similarities to achalasia. These findings demonstrate that viruses can induce achalasia-like pathophysiology and have renewed interest in the search for infectious agents in this enigmatic human disease.