We've historically determined an organization?s process maturity by conducting a maturity assessment that evaluates whether key process areas are documented and practiced. We've assumed that the higher the maturity level, the more cost effective the software development process. However, the maturity assessment doesn?t validate the critical assumption that cost is reduced and efficiencies are enjoyed; it validates only that KPAs are in place. This article examines evaluating process maturity on the basis of results, or the improvement in cost structure in the four quality-cost categories: prevention, appraisal, internal failures, and external failures.