Brazil relies on the Sistema Único de Saúde (SUS), a public health-care system used by nearly 65 per cent of the population. This article analyses the role played by accountability mechanisms in expanding access to primary health care in the municipality of São Paulo, Brazil’s largest city. Two accountability mechanisms are described and discussed: political competition and outsourcing. The article shows that from 2001 to 2016 the supply of primary care grew and the disparities in access to public health services decreased across the city areas with both the best and worst indices of income, education, and health. These distributive results are striking given how difficult it is to reverse inequalities, as attested by the findings of a number of studies in different parts of the world which indicate that the richest populations tend to persistently benefit more than the poorest from public spending on health.