The vast majority of gastrointestinal polyps are hyperplastic polyps or adenomas, their identification is possible bioptically. Adenomas are precancerous lesions, smaller ones with a diameter minor than 1 cm show invasive carcinoma in nearly 1%, in major polyps the percentage of invasive carcinoma will be 10% and more. Adenomas should therefore be removed with electrocautery snare (endoscopic polypectomy). Hamartomatous polyps (Peutz-Jeghers and juvenile polyps) are much less frequent, and mainly met with the Peutz-Jeghers syndrome (PJS) and familial juvenile polyposis (FJP). Hamartomas may bleed or induce obstruction or invagination. Adenomatous and malignant structures may be found within hamartomas, endoscopic polypectomy of these polyps is therefore mandatory. Mesenchymal (submucosal) polyps--leiomyoma, neurinoma--may only be identified by button-hole biopsy or after polypectomy; smaller submucosal polyps (up to 2 cm diameter) can be removed endoscopically, if strangulation is possible; the others should be removed during operation. Carcinoid tumors are rare within the upper and lower gastrointestinal tract, those with a diameter up to 1 cm should be removed by endoscopic polypectomy, larger ones have to be operated on.