This book presents an in-depth theoretically informed and empirically based studies of the efforts to introduce, use, and sustain the computer based Health Information Systems (HIS) in the local setting of Tanzania. Theoretically, the aim is to understand the relationship between processes of decentralization and sustainability of computer based HIS. I argue in this book that the key to achieving a sustainable HIS is to address the complexities and challenges of the decentralization processes of health services and HIS and their inter- linkages. In analyzing the case study through various concepts drawn from institutional theory and information infrastructure perspective, the book develops key insights towards addressing this paradox. The various implications developed from this work have implications for use in the study of decentralization and sustainability of IS generally and HIS more specifically in similar contexts.