Background/Objective: Achalasia is a motility disorder of unknown etiology, characterized by absent esophageal peristalsis and loss of lower esophageal sphincter relaxation. Balloon dilatation is the most effective non-surgical treatment for patients with achalasia. Manometry, scintigraphy and radiology are three techniques that provide an objective measure of success after balloon dilatation. The objective of this study was to determine the best predictor of success after balloon dilatation in patients with achalasia. Patients and Methods: 17 patients with achalasia of cardia who referred to Taleghani Hospital in 2003, were evaluated, both symptomatically and objectively (esophageal manometry, timed barium esophagogram, and scintigraphic emptying index), before and after treating with pneumatic dilatation of esophagus. The degree of patient symptom improvements after treat-ment was recorded and correlated with improvement in some indices derived by the above-mentioned three methods. Results: 12 (70.6%) of 17 patients had score improvements of ≥80%. All the pre-treatment diagnostic indices were significantly (P<0.05) different from those after therapy. There was no significant difference between the two groups in terms of improvement in symptoms according to the indices of barium swallow or scintigraphy. No association between the patient symptom scores and improvement in either the barium height or emptying index was found. Conclusion: In evaluation of efficacy of pneumatic dilatation of esophagus for treatment of achalasia, we should not only rely on transit or barium study.