Computer software maintenance consumes a large share of the federal government's automatic data processing (ADP) resources. A review was performed of computer software maintenance operations at 15 federal computer sites. Agencies have a limited overview of their software maintenance operations and have made little concentrated effort to effectively manage and minimize the resources required to maintain their computer software. ADP processing managers have done little to identify common causes of maintenance problems or reduce maintenance costs. The absence of maintenance management is due to the lack of a uniform definition of maintenance and the absence of government-wide guidance on how to control software maintenance and reduce its costs. Modifications account for about half of the total maintenance work load. While some modifications are necessary to adapt software to changing user needs, others occur because user needs are not properly identified in the first production version of the software. Agencies need to develop and implement policies and procedures which will increase maintenance efficiency and ultimately reduce the amount and cost of software maintenance required.