Despite the extensive literature on citizens' use of cognitive heuristics in political settings, far less is known about how political elites use these shortcuts. Legislative elites benefit from the efficiency of the accessibility heuristic, but their judgments can also be flawed if accessible information is incomplete or unrepresentative. Using personal interviews and a quasi-experimental design, this paper examines the use of the accessibility heuristic by professional legislative staff when assessing the importance of natural resources issues to their constituents. Staff members recall only a small subset of the relevant constituents in the district, and this subset is biased in favor of active and resource-rich constituents over other, equally relevant constituents. This paper provides a new application of cognitive psychology to political elites and addresses important normative questions about the importance of information processing for political representation. By drawing on the psychology literature on heuristics, this paper identifies the cognitive mechanisms of congressional representation and provides new evidence of old biases.