BACKGROUND/AIMS: Pneumatic dilatation of the oesophagus is a well established treatment for achalasia. Oesophageal perforation is the most serious complication that occurs in 2% to 6% of cases. The aim of this retrospective survey was to identify predictive risk factors for perforation in a consecutive series of 218 patients with achalasia. METHODS: Between 1983 and 1993, 270 pneumatic dilatations were performed in 218 patients. A Witzel dilator was used in 58 cases and a Rigiflex dilator in 212. Eight oesophageal perforations occurred (3%). The clinical, radiological, endoscopic, manometric, and technical data for the eight perforated patients were compared with those of 30 patients randomly sampled among those without perforation. RESULTS: All perforations occurred during the first dilatation. Perforations were fewer during dilatations with the Rigiflex dilator than with the Witzel dilator (2.4% v 5.2%). Perforations were all located above the cardia, on the left side of the oesophagus. In a multivariate analysis, a small weight loss and a high amplitude of oesophageal contractions in the group of patients with perforations were predictive of complications (respectively, p = 0.001 and p = 0.026). A contraction amplitude higher than 70 cm H2O in the lower part of the oesophagus was observed in three of eight patients with perforations but was not seen in any of the 30 patients without perforation (p < 0.01). CONCLUSIONS: This identification of risk factors should facilitate the choice between pneumatic dilatation or a surgical approach.