A family group of ten patients with the Peutz-Jeghers syndrome has been followed for a 27-year period. Eight members of the family had one or more manifestations of the syndrome. One member of the family died following a bypass procedure of a nonresectable carcinoma of the jejunum. Postmortem examination revealed this to be an adenocarcinoma of the jejunum arising in a Peutz-Jeghers polyp and metastases were present in the mesenteric lymph nodes. Two members of the family developed breast carcinomas, one arising in a fibroadenoma; both patients died, one of metastatic breast carcinoma, the other of a second primary malignancy (adenocarcinoma of the jejunum arising in a Peutz-Jeghers polyp). Three family members had benign ovarian tumors, one patient had a benign breast tumor and another patient had a benign colloid thyroid nodule. While the authors of this report believe that they have added a documented case of an adenocarcinoma of the jejunum arising in a Peutz-Jeghers polyp to the literature, the exact risk of intestinal cancer in the Peutz-Jeghers syndrome is unknown, but probably very small. Gastrointestinal surgery should continue to be performed in symptomatic patients and all patients should be followed closely at regular intervals.