Controversy surrounds the relative merits of radiotherapy and laryngectomy for the treatment of T3 glottic carcinoma. In this study of 82 patients with non-irradiated T3 glottic carcinomas managed by total laryngectomy, 45% had been clinically understaged and were pT4. There was a significant association between subglottic extension and tracheostomy with understaging. A trend to understage anterior commissure tumours was also evident. Nodal status did not influence understaging and therefore should not determine the choice of treatment of the glottic primary. Laryngectomy is recommended for patients with subglottic extension or a tracheostomy. If radiotherapy is to be used for the remaining tumours, then vigilance against understaging is required.