This paper presents data on the effectiveness of software fault insertion, discusses the advantages and risks of fault insertion, provides tips on gaining cultural acceptance for fault insertion and suggests high payback areas for fault insertion which have proven themselves over multiple products. In a typical software development cycle, defect detection starts to trail off once the mainline code stabilizes. With software fault insertion, it was found that the defect detection rate does not level off and the hardest task becomes not one of finding defects but one of prioritizing the stream of defects.