Impact of Rapid Expansion of the Estratégia de Saúde da Familia in Rio de Janeiro: Mixed Methods Evaluation The United Nations has recently set a target for countries to provide comprehensive healthcare at low cost to all citizens. While this is a welcome development, there are concerns that strengthening Primary Health Care (PHC) is not prioritised enough within national and international plans to achieve this. These concerns are grounded in knowledge that health systems with stronger PHC tend to have greater population reach, can respond better to local health needs, and provide a comprehensive set of benefits at lower cost. One potential reason for the lack of priority given to PHC is that most previous research in this area has been conducted in North America and Europe.  Brazil has invested in PHC over the last 20 years through the Estrategia Saude da Familia (ESF). The focus of the ESF is to re-orientate the Brazilian health system to PHC through the delivery of community based health care by multidisciplinary teams. The ESF is much less developed in large cities than rural areas, with poor populations living in favelas (urban slums) being especially underserved. ESF coverage was low (7% in 2008) in Rio de Janeiro until recently, but this has increased substantially since 2011(to 50% in June 2016) reflectings political ambition to achieve universal coverage in the city. The impact of ESF expansion in Rio de Janeiro on health outcomes and costs has important implications for how health systems in large cities in Brazil and internationally should be developed.  Our project will be conducted by a multi-disciplinary team of researchers and policy makers from Brazil, UK and USA, including doctors, health planners, mathematical modellers, and social scientists. It involves quantitative analyses of a unique database that has linked information from patients' medical records (both primary care and hospitalisation records), data on eligibility for state welfare benefits, and deaths in the city. This component of the project will examine whether public investment in ESF in Rio de Janeiro has produced better health outcomes, including a lower likelihood of being admitted to hospital for chronic conditions and a lower risk of death during infancy. It will examine whether individuals dually enrolled in the ESF and a major conditional cash transfer programme derive health benefits above those obtained from each programme in isolation. The project will also explore whether certain groups of patients, including from different race/ethnic groups, benefit more from the ESF than others. We will observe practices in health clinics and undertake interviews with health managers, clinicians, and patients to understand success in the implementation process and barriers to programme expansion. We will undertake mathematical modelling to estimate the potential benefits from further expansion of the programme in the city and whether comparable benefits may accrue if the ESF is expanded in other major Brazilian cities.  Our project aims to influence the development of PHC in Rio de Janeiro, other large cities in Brazil, and internationally by generating and actively disseminating timely evidence to policy-makers especially in a period of economical crisis. We will achieve this by including policy-makers and programme implementers from Rio de Janeiro in our research team. We will jointly host dissemination events with the Pan American Health Association in Rio de Janeiro and Brasilia with policy-makers from cities across Brazil to share the findings in order to inform policy development in the country and internationally. Our evaluation will provide important information to other countries seeking to achieve UHC in major urban areas and large cities, such as Colombia and India. By fostering links between academics and policy makers from Brazil, UK, and USA with extensive experience in analysing linked datasets, microsimulation modelling and qualitative research, we will build research skills and research translation capacity among all team members. The Global Challenges Research Fund (GCRF) supports cutting-edge research to address challenges faced by developing countries. The fund addresses the UN sustainable development goals. It aims to maximise the impact of research and innovation to improve lives and opportunity in the developing world.