In a testing service system (TSS) the activities that play a role in educational and psychological assessment are integrated and, as far as possible, computerized. Such systems will be the basis for test design, administration, analysis, and reporting in the next century. The main activities in a Testing Service System are item banking, item construction, test assembly, test administration, test analysis, and calibration. Testing service systems exist in various forms, ranging from general-purpose software packages to systems especially developed to support specific organizations and the administration of specific tests. With the advent of Windows technology, both individual professionals and testing organizations are more and more in a position to create a tailor-made TSS by linking existing software elements that have the functionality suited to the demands of the situation. In this paper, a number of the considerations that play a role in designing a TSS are described.