Two pairs of studies examined effects of perspective taking in communication, using a 2-stage methodology that first obtained people's estimates of the recognizability to others of specific stimuli (public figures and everyday objects) and then examined the effects of these estimates on message formulation in a referential communication task. Ss were good at estimating stimulus identifiability but were biased in the direction of their own knowledge. The amount of information in a referring expression varied inversely with the perceived likelihood that addresses could identify the target stimulus. However, effects were less strong than anticipated. Although communicators do take others' knowledge into account, the extent to which they do so involves a trade-off with other sorts of information in the communicative situation.