Emergency room residents face a range of clinical decisions and often call on senior residents or faculty members for help. The individual clinical decision process has frequently been analyzed, but little attention has been given to the social process in clinical decision-making. Based on data from interviews and over 100 hours of direct observation at two large urban general hospitals with busy emergency rooms staffed by medical and surgical residents, the authors suggest there are five basic decision situations. In each situation, the residents appeared to follow implicit decision patterns about involving other medical and surgical staff in the final clinical decision. The decision situations are nonacute, routine acute, nonroutine acute, multispecialty acute, and crisis. These situations call for individual, consultive, or consensual patterns in making decisions. The consequences of these patterns are explored. Improving residents' decision-making should contribute to improved understanding of the resident's role, better resident supervision, and better emergency room functioning.