The Greater London Authority, which provides London with its first directly elected Mayor, has important strategic powers and responsibilities that include a duty to improve the health of Londoners. This report considers how the GLA can best contribute to health improvement and to reducing health inequalities across the capital. It examines the powers and responsibilities of the Mayor and Assembly, the main health issues affecting Londoners, and the experiences of other city-wide authorities in the UK, North America and Europe. It analyses policy options and sets out recommendations for developing the role of the GLA in improving London's health.