The potential and limitations of laser photoablation of colorectal adenomas. Ablation of colorectal adenomas by Nd:YAG laser energy was investigated in 271 patients. Two hundred and forty-one patients, selected because of poor surgical and medical condition or refusal of surgery, presented with incompletely removed polyps or with lesions unsuitable for endoscopic polypectomy. Thirty patients with polyposis coli were treated for rectal stump polyps after subtotal colectomy and ileorectal anastomosis. Because of insufficient follow-up (28) or malignant degeneration (23), full evaluation was possible in 196 colon adenoma and 24 polyposis patients. Complete ablation with histologic confirmation for at least 12 weeks was achieved in 150 (82%) of the 183 colon adenomas. This declined to 141 (77%) because of later recurrences in prolonged follow-up. Treatment of large adenomas was less successful than that of intermediate and small lesions: ultimate ablation in 56, 85, and 93%, respectively. Impressive was the immediate relief in 100 symptomatic elderly patients, who were bothered by frequent diarrhea, excessive mucous discharge, and incontinence. All patients survived despite major complications (7%) that mainly consisted of stenosis and hemorrhage. Rectal stump polyps were eliminated in 20 patients with polyposis coli. The remaining four had an uneventful ileoanal anastomosis for ultimately uncontrollable growth of polyps. Malignancy was discovered in 22 adenoma patients and in 1 polyposis patient. We recommend laser ablation of colorectal adenomas for small and medium-sized polyps, that cannot be removed by endoscopic polypectomy in inoperable patients or in patients refusing operation. Laser treatment for extensive adenomas seems only appropriate for symptomatic relief. 