From October 1984 to March 1992, 21 patients of Hospital Nacional Guillermo Almenara Irigoyen-IPSS, Lima, Perú, with esophageal achalasia were treated with pneumatic dilatation using a 3.5 cm diameter Rider-Moeller balloon. The mean age was 40.5 years (range: 24-54). Six were men and 15 women. The mean time with dysphagia previous to treatment was 5.3 years. A total of 29 sessions were performed, 1.38 sessions per patient. The follow-up of the first 10 patients was carried for a mean time of 48.3 months (range:6-91). A satisfactory response to treatment was obtained in 8 patients (80%). Two patients (20%) relapsed after 2 and 3 treatment sessions needing surgery. One patient suffered a esophageal perforation recovering after surgical treatment. We conclude that pneumatic dilatation with Rider-Moeller balloon is a safe and not difficult medical procedure for esophagus achalasia.