Computer simulation of an information system prior to its implementation can predict time and workflow changes in a hospital department, while offering a common ground of communication across various levels in the organization. Often, the simulation can predict unexpected effects of changes to the work environment and allow experimentation with alternative scenarios at minimal cost to the department or the organization. In this paper we describe a discrete-event simulation experiment that predicted an unexpected increase in routine specimen processing time with the introduction of an information system in the HLA tissue typing lab at a major transplant center. The computer simulation enabled the reallocation of existing staff prior to the system implementation.