A retrospective analysis of two groups of patients, one surviving 16-20 years and the other dying within 10 years after diagnosis and treatment of primary breast cancer has been undertaken to determine whether there were particular clinical or histological features associated with long-term survival. The striking histological difference between the tumours of the two groups of patients was the prevalence of tumours of 'special' invasive types (cribriform, tubular, lobular and medullary) in the long-term survivors. Micro-invasive and non-invasive carcinomas were also more common in the survivors. The tumours of the surviving group which were not of a 'special' type more commonly had a better histological grade than those tumours of patients dying early from breast cancer. In the overall group elastosis was present in significantly more tumours of the survivors whereas tumour necrosis, vascular and lymphatic invasion were all significantly more common in the short-term survival group. Although there was a significantly increased incidence of earlier stage tumours in the long-term survivors, the histological distinctions between the two groups were independent of the differences in clinical features.