Silence and poor communication are known threats to patient safety. Despite efforts to promote teamwork and develop shared tools for communication, there are persistent gaps between nurse and physician practices. This study surveyed nurses and physicians working in labor and delivery units and discovered significant differences in their perceptions of patient harm associated with various clinical scenarios. These differences in patient harm ratings were the greatest predictor of speaking up, suggesting that differences in clinical assessment may serve as a useful target for intervention. The authors discuss the negative impact of environments where mental models are not shared, conflict is poorly managed, and disruptive behaviors stifle open communication. A past AHRQ WebM&M commentary discussed a case of "silence" when members of the operating room team were reluctant to speak up to a senior surgeon.