Aggregation is one of the key characteristics of information delivered by "information systems." It is important because the ability to design effective support systems depends to a great extent upon the degree of flexibility with regards to information aggregation that can be incorporated in the system. This paper sets forth a conceptual model of information aggregation based on the events theory of accounting. The model suggests that aggregation should be considered as a two-dimensional concept, comprising a temporal and sectional dimension. The two axes are further delineated in the form of "levels of summation" based on specified "events" of aggregation. These levels of summation representing various degrees of data aggregation could influence the value of the information delivered to a decision maker for a given "decision trait," namely, the "decision level" and/or "problem structure." This "events" model of information aggregation has important implications for the design of systems and future research.