Achalasia is the most common disease of esophageal motility. Most patients display a characteristic asthenic body habitus with weight loss as a prominent symptom. A small group of patients with achalasia present with obesity (defined as having a Body Mass Index >30). Only five cases of achalasia associated with morbid obesity have been reported in the literature. The objective of this study is to identify predisposing factors or behaviors that account for this enigmatic presentation. AIMS: To identify unique characteristics that allow individuals to overcome the limitation to caloric intake exhibited by the vast majority of patients with achalasia. METHODS: Fifteen patients (Group 1) were identified who met criteria for obesity (BMI>30) and achalasia (defined by esophageal manometry). This cohort was compared to two, age and gender, matched control groups; one group (Group 2) with achalasia alone, the second group (Group 3) with obesity alone. Patient demographics, symptom complexes, manometric data, and comorbid conditions were analyzed. The study group completed a questionnaire (73% response rate) addressing weight and diet history. RESULTS: More patients in Group 1 reported combinations of symptoms (dysphagia, regurgitation, chest pain) than in Group 2. Twenty seven percent of patients in Group 1 were men compare to an equal gender distribution in the population with achalasia. Although there appeared to be a bimodal distribution of lower esophageal pressures measured by stationary pull-through technique in obese patients with achalasia there was not a statistically significant difference with controls nor was there a correlation with BMI. CONCLUSIONS: To our knowledge this is the largest cohort of patients with achalasia and morbid obesity. Although rare, achalasia in obese individuals has significant implications. As more restrictive surgical procedures (roux-en-Y gastric bypass, LAGB) are performed for the treatment of obesity, it is imperative that these patients be identified. We were unable to identify manometric characteristics of patients with achalasia capable of reaching morbid obesity. Further physiologic and manometric evaluation may be needed to explain this paradox. This study supports careful history taking and complete manometric evaluation of patients with the constellation of obesity, dysphagia, regurgitation, and chest pain. Caution is warranted in selecting appropriate surgical treatment for obesity in this subset of patients.