This report summarizes the results of a research project commissioned by the Northern Ireland Housing Executive and BRE Trust to apply a methodology developed to calculate the cost of poor housing in England and Wales to the housing of Northern Ireland. This research shows that there is proportionately less poor housing in Northern Ireland than in England or Wales, largely due to the fact that Northern Ireland has the most modern housing stock of the UK nations. However, there is still an unacceptably high (and previously unreported) proportion of health and safety hazards in the housing of Northern Ireland. Although great strides have been made in improving the energy efficiency of the housing stock, the excessively high fuel prices in Northern Ireland meant that a very large number of households are still in fuel poverty. If works are targeted to reduce the worst health and safety hazards in these poor homes to an acceptable level, it is estimated that there will be a benefit to the National Health Service of some thirty-three million pounds per year. This figure could double if the definition of poor housing is widened to include all homes with a SAP (energy efficiency rating) of forty or less and target basic heating and insulation improvements on these homes. Dealing with fuel poverty will save even more.