Increased workload for nurses is associated with worsened patient outcomes, but similar studies of human factors affecting physicians have focused on the effects of shift duration and other organizational characteristics. This study from an academic medical center examined the effects of increased housestaff workload, defined as the number of new patient admissions and the overall team census, on inpatient mortality, length of stay, and costs. More admissions on the on-call day were associated with increases in all three primary outcomes. In contrast, an increase in overall team census was associated with decreased length of stay and lower costs. Although these findings are preliminary, the study adds important data to the ongoing debate on balancing patient safety and resident education.