The outbreaks of Severe Acute Respiratory Syndrome (SARS) in 2003, influenza A (H1N1) in 2009 and Ebola in 2014 have shown that increasingly infectious diseases can spread globally in a short timeframe, affecting both high- and low-income countries. Taking action to mitigate the impact of future crises relies on sharing public health surveillance data across national borders in an efficient and effective way. However, data users, particularly in high-income countries, often use surveillance data, particularly from low- and middle-income countries, with little or no benefit to the data generator. As Indonesia's refusal to share influenza virus sequences during the 2006 H5N1 outbreak illustrates, this imbalance increases reluctance to share and jeopardizes the global good that can be achieved. In order to share public health surveillance data internationally in an equitable way, technical, political, ethical, and legal issues need to be addressed. The Centre on Global Health Security at Chatham House is producing guidance that will address both the policy and technical issues with the aim of establishing new norms so that data can be shared in an open, transparent and equitable way.