OBJECTIVE To evaluate the outcome of patients with verrucous carcinoma of the larynx treated at the Princess Margaret Hospital with respect to control rates with radiotherapy, the salvage of local failure, the risk of regional lymph node metastasis following radiation therapy, and the risk of anaplastic transformation following radiotherapy. METHODS Forty-eight patients underwent primary treatment for verrucous carcinoma of the larynx in the period between January 1961 and December 1990. This represented 1.1% of cases of laryngeal cancer seen in this time period. Forty-three received radiotherapy and 5 had surgery as the primary treatment. Several radiation dose-fractionation schedules were used, the most frequent being 50 Gy in 20 fractions in 4 weeks (31 cases), while eight patients were treated with 55 Gy over 5 weeks. RESULTS The 5-year rate of local control was 59% for the 43 patients treated with radiotherapy. Surgical salvage was universally successful in all cases where it was attempted. The five cases treated with surgery alone did not experience relapse. Only one patient died of verrucous carcinoma. He had been medically unfit for surgical intervention at the time of initial treatment and at the time of relapse. He underwent a truncated course of radiotherapy (24 Gy in 3 fractions over three weeks in 1975). There was no evidence of increased neck relapse compared to other forms of laryngeal carcinoma following radiation treatment. No evidence to support anaplastic transformation of tumors treated with radiotherapy was evident in this series. CONCLUSIONS Local control using radiation treatment is less successful than with ordinary invasive and in situ squamous carcinomas of the larynx. Nevertheless, the treatment is effective and provides an appropriate option for laryngeal conservation, especially in advanced lesions where total laryngectomy may be the only treatment alternative. Surgical salvage of radiation failures contributes to very high rates of cure for verrucous carcinoma of the larynx. Anaplastic transformation of cases treated with radiotherapy was not observed in any case in this series.