By analyzing the practice of contemporary organizations, this paper explores the concept of virtuality as a nature of organizations. Drawing on research in organizational science and information systems, it proposes a framework containing six critical dimensions, which may be used as a basis to characterize, study and compare virtual organizations. These critical dimensions are purpose, connectivity, technology, boundary, business process and people. Two cases of virtual organizations are described to illustrate the concepts involved. Implications of this study and further research recommendations in this area are discussed at the end of the paper. This paper contributes to the conceptual discussion of virtual organizations and provides some important insights useful in the design of virtual organizations and the transformation of traditional organizations into virtual organizations.