Five patients with squamous or basaloid carcinoma of the anal canal have been treated with synchronous chemotherapy and external radiotherapy. Three were operable cases, of which one had abdominoperineal resection subsequently, while two had no surgery. The other two had a locally advanced inoperable tumour in one case and pelvic recurrence following abdominoperineal resection in the other. The chemotherapy regimen consisted of mitomycin C given as a single dose of 10 mg m-2 at commencement of radiotherapy and two i.v. infusions of 5-fluorouracil 1000 mg m-2/day for 4 consecutive days approximately 4 weeks apart. The radiation dose ranged from 50 Gy to 70 Gy in 25–35 fractions. All patients remain disease free with a median follow up of 14 months. Eradication of tumour at the primary site has been confirmed histologically in the three operable cases. A growing volume of data from the medical literature suggests that patients with operable carcinoma of the anal canal treated with this regimen have a probability of cure at least equal to that of abdominoperineal resection and have the advantage of retaining normal anal function and avoiding permanent colostomy.