This is an individual chapter of Theory of Constraints Handbook. The function of this chapter is to show how the Theory of Constraints (TOC) is utilized to improve the performance of a company while positively adding to enhancing its supply chain. The secret to becoming an agile company, much better reacting to the constantly altering demands of your clients, is having the ability to quickly respond to inescapable market variations. One way to achieve this is by taking a systems approach to take advantage of proven procedure improvement devices and thinking such as TOC, Lean and Six Sigma. This will result in a systems architecture that will direct and influence the way the company is managed. The change in the company will be extensive and like any improvement, some individuals will resist the need to change. So a central element of achieving this required change will be developing and successfully executing an aggressive paradigm shift with full involvement from the top level of leadership in the company. Regrettably, in the past there have actually been many failed improvement efforts that ignored this. Mistakenly, the conclusion was that the procedure improvements themselves were flawed. The failing was the company or their trusted consultants did not understand how they ought to be correctly utilized. Most of the times, the improvements were implemented within the company in seclusion and without comprehending the impact on their supply chain.