It has been common for both scientists and policy makers to view sanitary provision as a dichotomy between a centralised and a decentralised approach. Moreover, sustainability assessment has also been characterized by a dualistic approach, between the techno-centric and the eco-centric. Such views are often simplistic and not in tandem with the existing multiple sanitary options and service providers in East African cities, which defy such classification. This book provides the theoretical and empirical basis for a third way of classifying and assessing the multiple technical and institutional options to sanitary provision. This novel assessment approach called 'modernised mixtures' is used in this book as a tool for conceptualising, assessing and improving sanitary provision in East African cities. The assessment is based on four social and technical dimensions and three sustainability criteria. This inclusive approach in assessing sanitary mixtures, benefits decision making among imperfect options.