Twenty-four patients with colorectal carcinoma and one patient with a recurrent, transitional-cell, vesical tumor invading the rectum but not amenable to surgical resection underwent neodymium-YAG laser therapy. There were 16 men and nine women with an average age of 75.6 years (range, 35 to 93 years). There were 14, 6, 1, 1, and 3 tumors found in the rectum, rectosigmoid colon, transverse colon, descending colon, and ascending colon, respectively. Symptoms consisted of bleeding or partial obstruction. Twelve patients were high-risk surgical candidates, 11 patients had widespread disease, and two patients had another primary tumor not controlled by a previous surgical procedure. The tumor was eradicated in two patients. There were two complications, namely, a perforation and a rectovaginal fistula. Thirteen patients died from their disease. The remaining patients have been kept free from obstruction and bleeding.