This paper makes two main claims: first, that the need to protect health professionals' moral integrity is what grounds the right to conscientious objection in health care; and second, that for a given claim of conscientious objection to be acceptable to society, a certain set of criteria should be fulfilled. The importance of moral integrity for individuals and society, including its special role in health care, is advocated. Criteria for evaluating the acceptability of claims to conscientious objection are outlined. The precise content of the criteria is dictated by the two main interests that are at stake in the dilemma of conscientious objection: the patient's interests and the health professional's moral integrity. Alternative criteria proposed by other authors are challenged. The bold claim is made that conscientious objection should be recognised by society as acceptable whenever the five main criteria of the proposed set are met.