Often, past research on communication networks has assumed that perceptions of communication are isomorphic with observable communicative behaviors. If this assumption is invalid, as recent evidence suggests, then a description of the structure of participants’ perceptions is vital to attempts to link perceptions to observable communication. This study tests a descriptive model of perceptions of communication relationships between members of collectives. These perceptions are hypothesized to be the result of formal structure, collective interests, and individual interests. Linear models based on these ideas were tested in high and low uncertainty collectives, in which they accounted for 38% and 45% of the variance in perceived frequency of communication, respectively. Lack of predicted differences between the two organizations suggests that the structure of perceived communication relationships may be similar across organizations, whereas structure in observable communication may be the result of the way those relationships are activated.