The single-site study by Horwitz and colleagues (12), who analyzed changes that eliminated overnight call for housestaff, overcomes this problem. The investigators compared their teaching service with a preexisting nonteaching hospitalist service in the years before and after the new coverage. The teaching service changed the coverage system at their hospital so that “nocturnalists,” a cadre of attending hospitalists and moonlighting fellows, cared for newly admitted patients until the next day; in addition, they added a resident on day float service to the postcall team. Patients in the 2 services had different characteristics, but the results were not materially changed by statistical adjustment for demographic characteristics, insurance coverage, severity of illness, comorbid conditions, and case mix. On the teaching service, 3 of 6 measurable outcomes showed statistically significant improvement after the 2003 changes: intensive care use dropped, length of stay decreased, and fewer pharmacist interventions to prevent error occurred. Rates of discharge to home or rehabilitation were marginally higher, but short-term readmission rates increased. In the nonteaching hospitalist service, 4 measures worsened during the same period; no measure improved. In the comparison of adjusted outcomes between the 2 services, the teaching service had net, significant improvements in intensive care utilization, discharge to home or rehabilitation, and pharmacist interventions. The in-hospital mortality rate in the teaching service was 2.41% before and 2.03% after the regulations (P = 0.05); whereas in the nonteaching service it was 1.27% before and 1.10% after the regulations (P = 0.34).