The District Health Information System 2 (DHIS 2) is a complex health information system for collecting, analyzing and reporting health related data. DHIS 2 is free and open source and is implemented in many developing countries, such as Sierra Leone, Zanzibar, India and Vietnam. The Gambia implemented DHIS 2 autumn 2009/spring 2010 and is the case I present in this book. I had two field trips to the country during the spring 2010 assisting the Ministry of Health and Social Welfare in the implementation process. This book presents and analyzes the implementation process of DHIS 2 in the Gambia. The research goal was to explore how a complex health information system can successfully be implemented, maintained and used in a context with poor ICT knowledge. Conception-reality gaps when implementing a health information system play a vital role. Extensive training of health workers and computer technicians is also important to secure sustainability of the system. Data quality has been significantly increased after the implementation of DHIS 2 in The Gambia, and DHIS 2 has also proved more user-friendly than the previously used reporting tools.