Peutz-Jeghers syndrome is a rare hereditary disorder involving digestive polyposis with hamartomatous gastrointestinal polyps and mucocutaneous lentiginosis. We report three cases in which this syndrome was detected by complications: a massive rectal hemorrhage requiring a blood transfusion in one case and acute impaction of the bowel requiring emergency surgery in the other two. This work demonstrates the importance of the complications that may indicate that the patient has this syndrome. We also discuss the cancers of the digestive system and other organs that may be associated with PJS and recent progress in genetic research into this disease.