As a foundation for the design of groupware, we need a new science of group interaction, a systematic description of the processes at the group level of description that may contribute to problem solving, knowledge building and other cognitive tasks undertaken by small groups collaborating synchronously over networked computers. A scientific investigation of the knowledge-building interactions of online teams involves explorations along multiple dimensions: (a) designing a testbed to support interaction within teams, (b) analyzing how interaction takes place within this setting and (c) describing how the teams achieve their tasks. This paper discusses how a current CSCL project designed a groupware environment in which this could take place and be studied; it reviews how the project approached the rigorous study of what took place there; and it reflects on the nature of group interaction as an object for a new science. Categories and Subject Descriptors