The aim of this study is to contribute to the emerging field of health inequalities impact assessment. It develops further a conceptual framework that encompasses the policy context as well as the pathways leading from social position to inequalities in health. It then uses this framework for a comparative analysis of social policies and their points of potential impact on the pathways leading from lone motherhood to ill health in Britain and Sweden. The British General Household Survey and the Swedish Survey of Living Conditions are analysed for the 17 years from 1979 to 1995/96. First, the results show that the health of lone mothers is poor in Sweden as well as in Britain and, most notably, that the magnitude of the differential between lone and couple mothers is of a similar order in Sweden as in Britain. This is despite the more favourable social policies in Sweden, which our results indicate have protected lone mothers from poverty and insecurity in the labour market to a much greater degree than the equivalent British policies over the 1980s and 1990s. Second, the pathways leading to the observed health disadvantage of lone mothers appear to be very different in the two countries in relation to the identified policy entry points. Overall, in Britain, around 50% of the health disadvantage of lone mothers is accounted for by the mediating factors of poverty and joblessness, whereas in Sweden these factors only account for between 3% and 13% of the health gap. The final section discusses the implications of the findings for future policy intervention and research in the two countries.