The use of ICT for health, or e-health, is fundamental in health care delivery and public health practice. It has particular value in responding to shared global health challenges such as emerging epidemics or the health consequences of natural disasters. It is well documented that ICT is sorely lacking in countries that need it most: those countries most vulnerable to threats from diseases, disasters and poverty. Numerous country projects show the potential for improving use of ICT in public health, but the ability to plan and implement eHealth on a large scale, while adapting it to local health problems, presents a huge challenge particularly in countries in conflict and transition. Beyond the technology and financial challenges, countries need support in policy, priority setting and governance of ICT partnerships, which can be designed to benefit more than one sector.