Social justice is a policy aim of the UK Labour government. This paper considers the applicability of the concept to disability, seeking to establish principles for conceptualising social justice and disability and considering the nature of the challenges for public policy and society posed by this conceptualisation. The paper considers how disability is implicated in two types of claims about the source of social injustice: those concerned with socially constructed differences between people; and those arising from material inequalities. Appropriate values underpinning alternative conceptions of social justice are discussed and tensions in policymaking considered.