It can be argued that social interaction is a critical factor in understanding Web-mediated communication. While the concept and domain of social interaction has been studied in several disciplines they are underdeveloped in the current Web-enabled environment. This paper adopts a social psychological point of view of conceptual and operational issues in relation to social interaction. Through a review of the literature, two domains of social interaction are identified: task and socio-emotional interaction. The literature review also addresses some problems in defmition related to socio-emotional interaction. In an attempt to fill the gap between conceptual and operational defmitions of social presence, we redefme the construct and suggest new measures for social presence relevant to the current technology enabled environment. Inspired by concepts from the CulturaHistorical Activity Theory, the authors adopt a social psychology approach to this issue. This paper aims to initiate constructive discussion about the universal defmition and measurement of social interaction, in the context of Web-mediated communication.