Achalasia is a motility disorder of the esophagus characterized by aperistalsis, incomplete lower esophageal sphincter (LES) relaxation, and increased LES tension. Obstruction at the esophageal hiatus results in dilatation of the thoracic esophagus, which can cause coughing and dyspnea by compression of the trachea and main-stem bronchi, and predisposes the patient to regurgitation and pulmonary aspiration of stagnant esophageal contents. We report a case of slight aspiration pneumonia during anesthesia in a pregnant woman who had achalasia of the esophagus. Epidural anesthesia was performed for a cesarian section uneventfully. She had a regurgitation of the gastroesophageal contents after a thiopental 225 mg IV because she wanted to sleep due to anxiety. We performed endotracheal intubation with Sellick's maneuver immediately followed by suction. We regret not to have recognized that she had achalasia of the esophagus. Therefore, we did not remove the esophageal contents with a nasogastric tube. The result was that she had slight aspiration pneumonia.