Researchers and designers have been building awareness displays to improve the coordination of communication between distributed co-workers since the early 1990s. Awareness displays are technology designed to provide contextual information about the activities of group members. Most researchers have assumed that these displays improve the coordination of communication regardless of the relationship between the communicating parties. This article examines the conditions under which awareness displays improve coordination and the types of designs that most effectively support communication timing without overwhelming people with irrelevant information. Results from a pair of laboratory experiments indicate that awareness displays containing information about a remote collaborator's workload lead to communication attempts that are less disruptive, but only when the interrupter has incentives to be concerned about the collaborator's welfare. High-information awareness displays harmed interrupters' task performance, while abstract displays did not. We conclude that a display with an abstract representation of a collaborator's workload is optimal; it leads to better timing of interruptions without overwhelming the person viewing the display.