Abstract: A variety of tools can ease the difficult task of implementing multiuser user interfaces. In this paper, we identify them, classify them into different categories, motivate and describe the main concepts behind their design, point out the similarities and differences among the approaches implemented by them, outline the kind of multiuser interfaces they can support, and discuss the benefits and drawbacks of supporting each of these approaches. We provide a set of informal definitions for concepts that are common to these tools. We illustrate the tools by considering the implementation of an example multiuser user-interface using each of these tools. We evaluate them by considering how much automation they offer, how flexible they are, and how well they perform.