Diffuse leiomyomatosis of the esophagus is a rare condition and usually extends from the mid-esophagus to the proximal third of the stomach. Macroscopically, there is a marked diffuse thickening of the esophageal wall, with or without nodularity, predominantly affecting the circular muscle coat. Microscopically, the disorder is characterized by the loss of the normal orientation of the smooth muscle fibers of all three layers. We report a case in a 37-year-old woman which was incidentally discovered at exploratory thoracotomy.