The study analyzed how socioeconomic factors are associated with seeking, access, use, and quality of health care services in São Paulo, Brazil. Data were obtained from two household health surveys in São Paulo. We used logistic regression to analyze associations between socioeconomic factors and seeking, access, use, and quality of health care services. Access to health care services was high among those who sought it (94.91% in 2003 and 94.98% in 2008). The proportion of access to and use of health care services did not change significantly from 2003 to 2008. Use of services in the public sector was more frequent in lower socioeconomic groups. There were some socioeconomic differences in seeking health care and resolution of health problems. The study showed almost universal access to health care services, but the results suggest problems in quality of services and differences in quality experienced by lower socioeconomic groups, who mostly use the Brazilian Unified National Health System (SUS).334