Krishnan and colleagues have conducted a prospective clinical trial of a weaning strategy previously demonstrated to enhance clinical outcomes of mechanically ventilated patients. They draw conclusions quite different from those drawn in an accompanying editorial. Krishnan and colleagues compared the outcomes of patients supported with mechanical ventilation for at least 24 hours. The outcome of those patients weaned from mechanical ventilation was compared with the outcome of those patients who received usual care. Although usual care was not defined, it was delivered in an unusual environment that included many systems improvement elements previously demonstrated to improve clinical outcomes. The investigators worked in a closed intensive care unit that employed large numbers of physicians (six residents, two postdoctoral fellows, and two attending physicians for a 14-bed unit), and used a structured standard checklist to make patient review during rounds more systematic. These features might reduce the difference in outcome between the protocol group and other patients in their unit. In addition, the experimental design allowed convergence of the method of care of protocol group patients with the method of care of other patients. Their results are compatible with either no effect of the protocol or with an inability to demonstrate the effect of the protocol because of the systems improvement elements in operation in their intensive care unit.