This book provides an introduction to the positive theory of the budgetary process based on the theory of public choice. Although budgetary institutions are very diverse, both between and within countries, the author identifies key elements in the budgetary process that are common to all forms of representative government. The book develops a step-by-step model that can be used to explain and predict budgetary decisions in existing institutions, as well as to analyze institutional change, including cost budgeting and various forms of privatization.