This study examined whether receiving care from locum tenens (short-term substitute) physicians in hospital internal medicine practice affects patient outcomes. The concern is that discontinuity might increase risk for adverse events. This retrospective observational cohort study of Medicare patients found no differences in 30-day mortality in those treated by locum tenens physicians compared to those who were not exposed to any substitute physicians. While costs and length of stay were higher for patients with substitute physicians, readmission rates were lower. The authors conclude that locum tenens physicians do not adversely affect safety outcomes like mortality.