Zero Base Budgeting (ZBB) is an approach to budge formulation that facilitates the analysis of budget requests and proposals from the bottom up. It consists of a set of conceptually simple techniques aimed at increasing the visibility of ongoing or previously funded activities and making them compete on a more equal footing with proposals for program expansions or entirely new program efforts. This paper describes how ZBB seeks to achieve this objective by exploiting, rather than fighting, the principle that in a large public organization the key budget decisions are considered marginal. Because of the sheer size and complexity of most public agency budgets, no person or group can scrutinize and make a decision on the proper disposition of each and every dollar. Therefore, during the formulation of a budget, the attention of policy makers tends to be focused on relatively new funding decisions and these decisions cluster around the margin of available revenue. This paper describes the concept of Zero base budgeting.