This study evaluates a vendor supplied structured methodology which was implemented in a large manufacturing organization. Thirty projects using the methodology are measured for efficiency and effectiveness of software maintenance performance. The performance of these projects is evaluated using both objective metrics and subjective measures taken from stakeholders of the software applications. The performance results of these thirty systems are then contrasted to the performance results of thirty-five applications in the same organization that do not use this structured methodology and to one hundred sixteen applications across eleven other organizations. All of these applications had been in operation at least six months when they were studied. The software applications developed and maintained using the structured methodology were found to have some significant cost and quality performance gains over the applications that do not use this methodology