Dogs can play an important role in their owners’ lives. As well as providing a source of comfort, emotional support, and entertainment, there is now evidence suggesting that dogs may promote their owners’ health. The mechanisms of these beneficial effects, however, are unclear. The important role of dogs in their owners’ medical emergencies is illustrated by two cases of patients admitted to our intensive care unit, in whom untrained domestic dogs saved lives by alerting the family. Companion dogs may react to emergencies of their owners and save lives. Clarifying how dogs perceive medical emergencies might stimulate design of emergency alarm systems.