Women's unpaid work at home has not concerned theorists of social justice, despite the fact that it renders women vulnerable to exploitation and hence to social injustice. Based on a critical analysis of three conceptions of work and women's work in the materialist tradition of thought - Marx, the domestic labour debate, and Delphy and Leonard - the author develops her own theory of women's work as care. By focusing on the material, psychological and gendered aspects of care, the theory elucidates how and why care is exploitative as long as it remains women's work, and what problems it poses for conceptions of social justice. It also enables the author to develop a striking new interpretation of the much discussed ethic of care: how it relates to considerations of justice and the place it has in moral and political philosophy.