This paper reports the development of a mathematical model that can be used to simulate information overload. A decision maker is posited, whose task it is to evaluate units of information arriving at random times. The decision maker forms an opinion, based on the (possibly inconsistent) indications of the considered information. This information may or may not be relevant to his or her task, and any unit might or might not accurately indicate the true situation. Determination that a unit of information is irrelevant takes a small amount of time; evaluation of relevant information takes longer. The elapsed time to a prescribed level of confidence provides a metric of decision maker efficiency. The subject's effectiveness depends on how frequently relevant information is presented and to what extent he or she is distracted by the accompanying irrelevant data. The model permits prediction of the optimal rate of presentation of relevant reports as well as analysis of the effects of distracting data on decision maker effectiveness.