Medical trainees are likely supervised more closely than in the past, in part due to regulations passed in 2003 that limited housestaff work hours. This study used direct observation of emergency medicine and internal medicine teams to derive a conceptual model of the types of housestaff supervision. Senior physicians engaged in various types of oversight, including "routine oversight" (preplanned meetings with housestaff such as daily rounds), "responsive oversight" (triggered "double-checking" of patients' clinical condition), and "backstage oversight" (monitoring of which the trainees were unaware, such as checking lab values). The authors suggest that this framework could be used to evaluate the effects of different types of supervision on patient care and housestaff education. A previous commentary discussed the potential positive and negative aspects of increased oversight by senior staff.