A retrospective clinico-pathological study has been carried out in a series of 405 patients with squamous cell carcinoma of the head and neck who underwent a total of 484 radical neck dissections. The recurrence rate in the neck in 327 patients who had histological positive nodes was 21.1%. Recurrence in the neck after a standard radical neck dissection almost invariably proved fatal. A statistical analysis has been carried out to evaluate the clinical and pathological factors which are of importance in regards to recurrence in the neck. Histological factors such as extra-nodal spread and the number of histological positive nodes have been shown to be of much more prognostic importance than clinical parameters. When corrections are made for interdependencies between variables, histological extra-nodal spread proved to be the most important single prognostic factor (P less than 10(-7)).