1. Achievement of the best results in the treatment of patients with cancer of the breast is dependent upon the employment, in the most suitable manner, of surgery and radiation therapy. These two modes of therapy should be thought of, not as competitory, but as complementary agents. If they are to be used well it is necessary to classify the cases into somewhat arbitrary groups; such a classification has been suggested.2. Radiation may improve the results of inadequate surgery but should not be looked upon as a substitute for adequate surgery.3. Age does not seem to be an important factor in prognosis.4. The case for routine sterilisation of women in the pre-menopausal period has not been proved.5. Pregnancy in women whose disease has been treated effectively has not much influence upon the prognosis in the series of cases surveyed.6. The clinical index of malignancy herein described, provides a very accurate formula for the summing up of the more important factors which have to be taken into consideration in planning the management of any case and is a reliable guide to prognosis.7. Radiation achieves its greatest triumphs in the control of extensive primary disease. The over-all figure of 47 per cent freedom from disease at the end of five years appears, on paper, considerably lower than is actually the case, because of the inclusion of so many cases that would formerly have been considered hopeless.8. A general plan for the management of cancer of the breast is suggested, including new and somewhat strict criteria of operability, which, if adopted, it is believed would bring about a substantial general increase in five-year survivals, a reduction in post-operative recurrences, and other very considerable benefits to the patient.