Surgeons are guided in their decisions by personal experience, and by their ability to critically appraise evidence in the literature. High quality studies of discrete surgical treatment options and outcomes are not always available. In such circumstances decision analytic modelling can be used to mathematically translate a complex clinical scenario, and its components, into outcome pathways to guide surgical decisions to maximize final health related outcomes for the patient, or to guide the design of future studies to clarify optimal surgical decision making. Decision models utilize decision trees whereby all possible treatment outcomes for a given strategy are compared and assigned a value such as probability of occurrence, utility, Quality-Adjusted Life Years, cost, benefit or other desired outcome comparative. A base case scenario is created for the primary model and the robustness of this model is then determined through single or multi-way sensitivity analysis. The following chapter will guide the reader on how to interpret and appraise a decision analysis study.