Abstract
An examination has been made of 12 tumours of the bronchial tree other than carcinoma. These have been classified on a histological basis as carcinoid tumours and cylindromas. Their microscopical structure, origin, situation and form of growth have been described and their degree of malignancy evaluated. Their relation to bronchogenic carcinoma has been examined, and the carcinoid group has been compared with carcinoids of the gut. The possible relation of carcinoid to cylindroma is discussed, and the validity of the adopted nomenclature is shown.