The duty to provide care is foundational to the nursing profession and the work of nurses. Unfortunately, violence against nurses at the hands of recipients of care is increasingly common. While employers, labor unions, and professional associations decry the phenomenon, the decision to withdraw care, even from someone who is violent or abusive, is never easy. The scant guidance that exists suggests that the duty to care continues until the risk of harm to the nurse is unreasonable, however, “reasonableness” remains (...) undefined in the literature. In this paper, I suggest that reasonable risk, and the resulting strength of the duty to provide care in situations where violence is present, hinge on the vulnerability of both nurse and recipient of care. For the recipient, vulnerability increases with the level of dependency and incapacity. For the nurse, vulnerability is related to the risk and implications of injury. The complex interplay of contextual vulnerabilities determines whether the risk a nurse faces at the hands of a violent patient is reasonable or unreasonable. This examination will enhance our understanding of professional responsibilities and can help to clarify the strengths and limitations of the nurse's duty to care. (shrink)