A longitudinal study is being conducted of a clinical laboratory computer information system's impact. This paper reports on effects that laboratory directors anticipated prior to installation, and effects reported by laboratory technologists 7 months postimplementation. Primary changes caused by the computer system were increases in the amount of paper work performed by technologists, and improvements in laboratory results reporting. The system generally was well accepted, but laboratory technologists differed in their responses to it. Technologists in some laboratories focused on work increases, whereas in other laboratories they emphasized improved information flow. The paper considers how changes in processes and outcomes of work might affect responses to a computer system. It also considers the implementation process, and suggests some areas where management could benefit from an improved understanding of responses to a computer information system.