There is very little information on differences in mortality by socio-economic group in Ireland. Only one major study has been done in this area. That study was based on data for 1981 and confined to aggregate deaths for males aged between 15 and 64. The objective of this paper is to extend the previous work along a number of important dimensions. Combined deaths data for males for the period 1986-1991 are used, thereby allowing differentials to be estimated with more precision. Mortality differentials for males by cause of death are also explored using this data. Methodological issues associated with trend analysis are highlighted in the paper. There is some discussion on both causal relationships and policy implications arising from analysis of the data. The results confirm international trends in this area: poorer people have higher mortality relative to people in more advantaged circumstances.