Agriculture can serve as an important engine for economic growth in developing countries, yet yields in these countries have lagged far behind those in developed countries for decades. One potential mechanism for increasing yields is the use of improved agricultural technologies, such as fertilizers, seeds and cropping techniques. Public-sector programs have attempted to overcome information-related barriers to technological adoption by providing agricultural extension services. While such programs have been widely criticized for their limited scale, sustainability and impact, the rapid spread of mobile phone coverage in developing countries provides a unique opportunity to facilitate technological adoption via information and communication technology (ICT)-based extension programs. This article outlines the potential mechanisms through which ICT could facilitate agricultural adoption and the provision of extension services in developing countries. It then reviews existing programs using ICT for agriculture, categorized by the mechanism (voice, text, internet and mobile money transfers) and the type of services provided. Finally, we identify potential constraints to such programs in terms of design and implementation, and conclude with some recommendations for implementing field-based research on the impact of these programs on farmers' knowledge, technological adoption and welfare.