Charles Tilly presents a powerful new approach to the study of persistent social inequality. Acknowledging that all social relations involve fleeting, fluctuating inequalities, he concentrates on those inequalities that last, often through whole careers, lifetimes, and organizational histories - durable inequalities. How do such long-lasting, systematic inequalities in life chances arise, and how do they come to distinguish members of different socially defined categories of persons? Exploring the nature, forms, and functioning of representative paired and unequal categories such as male/female, black/white, and citizen/noncitizen, Tilly argues that the basic causes of these and similar inequalities greatly resemble one another. In contrast to the case-by-case explanations that prevail in contemporary analyses of inequality, his account is one of process. Categorical distinctions arise, Tilly says, because they enable people who control access to value-producing resources to solve pressing organizational problems. Whatever the "organization" is - as small as a household or as large as a government - the resulting relationship of inequality persists because parties on both sides of the boundary dividing the categories come to depend on that solution, despite its drawbacks.