Patient with achalasia have a 10-50 fold increased risk to develop esophageal squamous cell carcinoma (ESCC). Early diagnosis of ESCC is essential, and detection of an earlier dysplastic stage is preferred. Endoscopic detection is however difficult and often delayed. Chromoendoscopy with Lugol dye increases detection rates dysplasia and ESCC to 91-100%. The aim of this study was therefore to evaluate a screening program using chromoendoscopy with Lugol to detect dysplasia in patients with idiopathic achalasia. A second objective is to study the relationship between foodstasis and the development op dysplasia