Abstract Using data routinely published by the Registrar General in Northern Ireland,standardised mortality ratios were calculated for each of twenty-six local government districts across a range of causes of mortality. A descriptive account of these is provided, and attention is drawn to significantly high or low SMR's. A number of social variables were extracted from the 1981 census for each local government district. An investigation of the relationship between these and the SMR's was carried out. Cerebro-vascular disease and the category of ‘other heart disease’ caused markedly high death rates in rural areas and were associated with unemployment and overcrowding as measured by census variables. Lung cancer caused high death rates in urban areas with significantly high rates only in Belfast and Londonderry. Ischaemic heart disease showed very variable patterns across the Province, but it was not possible to explain or interpret these in terms of any of the variables studied. It is thought that other factors such as diet or smoking may be important in explaining the variations observed. It is concluded that the findings of this study suggest the need for further investigation of the relationship between social disadvantage and high mortality rates for certain diseases, since high levels of both are experienced in parts of Northern Ireland.