Health Information Systems (HIS) are a critical component of a health system, but have often been neglected in most developing countries. The Health Information Systems Programme (HISP) tries to remedy this, by working closely with end users to improve HIS and thereby increasing the use of information. Its main vehicle for this is the District Health Information System, version 2 (DHIS2), a flexible open source software tool based on web technologies, that can be used for collecting, validating, analysing and presenting health data. The objective of this thesis is to study how a complex information system like DHIS2 can be implemented in a developing country. My main focus is West Africa, where I have spent about four months doing fieldwork. Most of the time I have been in Ghana, assisting and studying the implementation of DHIS2 there. As part of this, I have evaluated the Ghana health information system in general, and participated in the implementation of DHIS2 there. While Ghana is the main focus of my research, I have also worked with other countries in the region, in particular with Liberia. Consequently, I also discuss and evaluate the situation in terms of health information for the region as a whole. I show how the internet can play a huge for the ICT development in Africa in the coming years. Contrasting the implementations in Ghana and Liberia, the former using the internet and the latter using standalone installations, demonstrates the many benefits internet can have when implementing a system like DHIS2, for example by increasing the possibility of user participation in the design of the system and reducing the need for local human capacity to support software installations.