Nursing, perhaps more than any other health care profession, claims caring as fundamental to its practice. Professional vigilance is the essence of caring in nursing. This article uses historical and theoretical bases to define professional vigilance and discuss its components. Two types of nursing diagnoses, central and surveillance, are proposed. Central diagnoses indicate the need for the nurse to plan and implement interventions for the achievement of outcomes. North American Nursing Diagnosis Association (NANDA)-approved diagnoses fall in this category. Surveillance diagnoses are those that recognize patient risks that are anticipated by the nurse, who remains ready to act in the event of occurrence. The profession, as a whole, and language developers, in particular, need to expand standardized nursing diagnosis terminology so that the contribution of nurses' vigilance to patient safety may be effectively communicated and documented.