This book presents Organisational Sustainability Modelling (OSM), a new method to model and analyse risk and return systematically for Cloud Computing. Return includes improvements in technical efficiency, profitability and service. Risk includes controlled risk (risk-control rate) and uncontrolled risk (beta), although uncontrolled risk cannot be evaluated directly. Three OSM metrics, actual return value, expected return value and risk control rate are used to calculate uncontrolled risk. The OSM data collection process in which hundreds of datasets are used as inputs is explained. Outputs including standard error, mean squared error, Durbin-Watson, p-value and R-squared value are calculated. Visualisation is used to illustrate quality and accuracy of data analysis. The metrics, process and interpretation of data analysis is presented and the rationale is explained in the review of the OSM method. Three case studies are used to illustrate the validity of OSM. All three case studies confirm there are benefits for the adoption of Cloud. Together these demonstrations answer the two research questions for this book. OSM has been adopted by several organisations.