The adoption of medical emergency teams (METs) has generated significant controversy over their evidence and effectiveness. This study analyzed more than 100 MET calls at a university hospital and discovered that 44% of them were delayed based on pre-established criteria. Investigators found that these call delays were more common on night shifts and were predicted by shift and patient–unit mismatches. The authors suggest that their findings call for attention to factors other than simply nurse staffing ratios when devising policies to promote patient safety.