This paper describes analysis techniques used to assess quantitatively the software maintenance process of a large military contractor, and the results obtained. The analysis techniques make use of basic data collected throughout the maintenance process. The data collected are extensive and allow the effects of adding a set of functional enhancements to be traced to process activities and product impact. The analysis techniques include data snooping, applied to gain insight into relationships and trends in the data. Simple nonparametric statistical techniques are then applied to test relationships between data items. The results provide valuable information for predicting process and product characteristics, and assessing the maintenance process.