This paper describes a model of information retrieval as social interaction, which distinguishes between three types of information interaction goals: those which are: 1) task and 2) topically oriented; and those which are 3) centered around situation assessment. The concept of situation assessment (SA) refers to a process of situational inference in which people attempt to understand the social dimensions of the interaction space they are in. Based upon the theory of social interaction, four dimensions of SA are identified: assessment of 1) self-performance; 2) norms of interaction; 3) communication conventions; and 4) intersubjectivity. An empirical investigation of the nature of situation assessment was conducted in one new information retrieval environment. Fifty experienced online searchers performed searches using an IR system that contained several features that were new to them. Verbal protocol data were content analyzed for the appearance of assessment expressions. Results of this study suggest that situation assessment is an important cognitive activity in new information retrieval environments. SA expressions appear more frequently than do those related to either task or topical relevance. At the same time, situation assessment is found to be negatively associated with one performance measure looked at here - number of documents saved by searchers. Implications of these results for IR theory and system design are discussed in the conclusion.