One of the most misunderstood elements in ISO 9001 is clause 4.14. The element discusses the requirements for corrective and preventive action. In many ways the two are related, but there are several differences that need to be clarified. Properly understood, documented and implemented, these two actions are probably the most powerful continuous improvement tools an organization can utilize, whether implementing ISO 9000, QS-9000 or just improving the internal quality management system. This paper will identify the differences between corrective and preventive action and will define methods that can be used to implement an effective corrective and preventive action system.