Objective The definite diagnosis of esophageal achalasia is established using manometry, which is performed in patients with suspected achalasia based on the findings of screening examinations, such as upper gastrointestinal endoscopy, chest computed tomography (CT), or a barium swallow test. However, the exact values of test characteristics in these supportive diagnostic examinations remain unclear. Methods We estimated the sensitivity and specificity of characteristic findings in the supportive diagnostic examinations for achalasia by comparing the data of a large number of achalasia patients and others with digestive symptoms. Patients Achalasia patients (n=119) and non-achalasia patients with suspected achalasia and repeated feelings of chest discomfort (n=37) who were treated in a single university hospital. Results Characteristic findings on chest CT (i.e., dilated esophagus, air-fluid level formation) and barium swallow tests were observed in more than 80% of achalasia patients but in less than 10% of non-achalasia patients. In contrast, conventional characteristic findings of upper gastrointestinal endoscopy (i.e., intra-esophageal food debris, feeling of resistance at the esophagogastric junction) were seen in only 40-70% of achalasia patients. In particular, the feeling of resistance at the esophagogastric junction was observed by the examiner in only 30-50% of patients. Conclusion Intra-esophageal food debris or resistance at the esophagogastric junction on upper gastrointestinal endoscopy will be positive in only about half of patients with achalasia. Other supportive diagnostic examinations, such as chest CT or barium fluoroscopy, should therefore be included in order to avoid overlooking the disease.