Wynne Griffith, G. (18 Victoria Terrace, Beaumaris, Anglesey, Gwynedd, North Wales). Cancer Surveillance with particular reference to the uses of mortality data. International Journal of Epidemiology, 1976, 5: 69–76. Cancer surveillance serves several purposes related to prevention, control and treatment. Morbidity information from cancer registration and mortality data based on death certification complement each other and both are necessary for surveillance. In many respects mortality data are sufficiently accurate and specific to reveal major differences and trends. The importance of recognizing even small aggregations of rare tumours is stressed.