"Tail-Splitting" is a new technique to identify defect prone modules by enhancing the focus of the Pareto distribution by a development process factor. The simple yet powerful influence of a varying tail membership as a function of development process phases is captured by the tail-split-string which tags each module. The case studies on an operating systems product demonstrate that the tailsplit- string identifies a small set of modules with a high probability of field failure. The tail-boundary in the algorithm provides for a natural tuning parameter to control the size of the identified set to suit the resources available for rework. Release managers have found that the method is particularly useful to sift modules, with low false positive, for late stage rework.