The range of application of Nd:YAG laser is now wide and of particular interest in the treatment of neoplastic lesions of the large bowel, both benign and malignant, which, besides the debilitating of vegetative lesions, may also provide a good hemostasis of the bleeding ones. Yag laser treatment of malignancies is indicated in patients not suitable for surgery due to the extent of the disease or to the high anesthesiologic/surgical risk. The treatment of choice for benign neoplasms is represented by endoscopic polypectomy, being Yag laser therapy reserved to patients with very large polyps and with a high anesthesiologic risk. Yag laser therapy is also recommended in teleangiectasies with active or previous bleeding, since it allows the complete ablation of such lesions with subsequent outstanding hemostasis. Furthermore this treatment may be advantageously associated to other operative endoscopic procedures, such as diatermotherapy, dilatation and injection therapy. It is also to be outlined that Yag laser therapy is currently used to cure benign diseases and for the palliation of advanced cancer in inoperable patients. Our laser instrument is an Nd:Yag laser MBB Medilas 2 with maximum power of 100 watts at the tip, with 'non-contact' laser fibers. We use flexible optic fiberendoscopes of several sizes, according to the type of lesion to be treated. Moreover we have employed both Savary dilators of progressive caliber from 5 to 15 mm and Rigiflex pneumatic balloons. Adequate bowel preparation by means of isosmotic solution was achieved in patients with non stenotic neoplasm, or evacuative enemas and fluid diet in patients with bowel neoplastic stenoses. The patients were premedicated with benzodiazepines. Stenotic malignant lesions have been treated with endoscopic dilatation before laser treatment. At each session 4,000 - 8,000 joules of energy were administered; all patients received an average of 5 - 6 laser sessions. Followup laser sessions have then been preformed every 2 months. From November 1st, 1992 to February 28th, 1995, 130 patients (78 males and 52 females) with an average age of 65 years (range 39 - 91) underwent Nd:Yag laser therapy of the large bowel for a total of 722 laser sessions. In 91 patients suffering from colorectal cancer with a mean extension of 5 cm 492 Nd:YAG laser sessions were performed with an average of 5.4 sessions per patient (range 1 - 19).