In some ways, this splendid conference marks the end of a road and I doubt if another will be held under the same title. Not that there is not much fundamental work still to be done on the mechanism of oestrogen action and its effects on normal and diseased breast tissues, but its general role in relation to breast cancer would appear now to be clear. Oestrogens are necessary for the development of the normal human breast, for the initiation and promotion of breast cancer, and may even act as a mitogen in established disease. But their role can be regarded as largely permissive. It is not clear that excess oestrogens are in any way causative of breast cancer in humans.