Over a 10 year period, 530 patients were treated at the Lille Laser Center for a rectosigmoid tumour. Both argon and Nd:YAG lasers were used. Two hundred patients were treated for palliation of symptoms from a rectosigmoid cancer, 313 patients were treated for a rectosigmoid villous adenoma, and 17 patients with a familial polyposis were treated for the rectal polyposis remaining after total colectomy. The immediate success rate and complication rate were 88% and 2.7%, respectively, for patients with advanced cancer, 92% and 2% for those with a villous adenoma, and 100% and 0% for those with polyposis. Patients with an advanced cancer remained functionally improved during a 10.1 month average period after initial improvement. The recurrence rate after initial treatment for villous adenomas was 14% during a 3.1 year average follow-up. Immediate results were influenced by reason for treatment, initial symptoms and circumferential extension for patients with a cancer, and only by circumferential extension for patients with a villous adenoma. Long term results were influenced by reason for treatment and circumferential extension for patients with a cancer, and by reason for treatment, initial histology and localization for patients with a villous adenoma.