Defect tracking is a critical component to a successful software quality effort. In fact, Robert Grady of Hewlett-Packard stated in 1996 that “software defect data is [the] most important available management information source for software process improvement decisions,” and that “ignoring defect data can lead to serious consequences for an organization’s business” [Grady96]. However, classifying defects can be a difficult task. This report discusses five defect categorization and analysis efforts from four different organizations. This list of organizations should be taken as a sample of the range of schemes covered in research and in industry over the previous twenty-five years. The analysis efforts at these organizations generally focus on one of three goals: finding the nature of defects, finding the location of defects, and finding when the defects are inserted, with the intent of using this information to characterize or analyze the environment or a specific development process. At the conclusion of this discussion, the results of two surveys covering the defect classification and analysis practices of approximately 30 companies are presented. These surveys give some insight into how industry is currently handling this complex issue. Finally, section III of the report presents some suggestions of how companies could begin or expand their defect classification efforts.