We analyze the incidence and evolution of the early complications of 96 consecutive patients with primary esophagus motor disorders, treated with pneumatic dilatation under endoscopic control (1.4 sessions per patient). In 4 (0.042/patient, 0.029/dilatation) patients the esophagus was perforated; the diagnosis was made in the first 24 hours; pneumomediastinum was a constant finding in the radiological exploration. In three cases the complication was suspected because of the apparition of sustained thoracic pain after the dilatation maneuver and in one case the presentation symptom was bleeding of cardial mucosa, larger than usual, at the end of the dilatation. The four patients evolved favorably with conservative treatment (avoidance of oral food intake, gastroesophageal aspiration, antibiotic therapy and parenteral nutrition).