Research in ICT4D is a constant search to answer the question of how ICT fosters development in underdeveloped communities. While many theories have guided research, we are yet to develop a cumulative body of knowledge to answer this question. In this paper, we argue that the elusive link between ICT and development needs to be grounded in three groups of theories: theories to understand development; theories to understand ICT; and theories to understand how ICT make development happen. We present exemplars of theories from each group, and illustrate how we have used them in our research. Through reflecting on which questions to be answered by including the three groups of theories, we propose research agendas.