We report a rare case of achalasia coexistent with megacolon. The patient, a 25-year-old woman, presented at our hospital with a history of abdominal pain with distension, and was finally operated on for a megacolon. Five months later she presented symptoms of progressive dysphagia and heartburn. Oesophageal manometry of the upper and lower oesophageal sphincter and X-ray studies showed images compatible with achalasia. Oesophagomyotomy of the oesophagogastric junction (Heller procedure with Dor haemifundoplication technique) was performed. In the specimens taken for biopsy, neither pathology of the myenteric plexuses, nor atrophy of the muscle fibres was evident. Chagas' disease serological diagnosis for Trypanosoma cruzii, neurological disease, diabetes and all the pathological events related with neuromuscular disorders of the gastrointestinal tract proved negative. We believe that the pathological findings are related to a dysfunction of the physiological mediators of the upper and lower digestive tract motility. The present case is extraordinary and, to our knowledge, extremely rare. The association of the two pathological diseases is questionable, and the literature is reviewed.