Effective interventions exist for many priority health problems in low income countries; prices are falling, and funds are increasing. However, progress towards agreed health goals remains slow. There is increasing consensus that stronger health systems are key to achieving improved health outcomes. There is much less agreement on quite how to strengthen them. Part of the challenge is to get existing and emerging knowledge about more (and less) effective strategies into practice. The evidence base also remains remarkably weak, partly because health-systems research has an image problem. The forthcoming Ministerial Summit on Health Research seeks to help define a learning agenda for health systems, so that by 2015, substantial progress will have been made to reducing the system constraints to achieving the MDGs.