This theoretical study considers, briefly, the situations of nurse practitioner and patient and their relationships, within the wider setting of nursing practice. It considers an ideal type of nurse/patient process in a way which ignores a whole range of what, relative to the ethical and technical standards of the best practitioners, are substandard deviant practices. The study reveals two important consequences of the features of the patient situation for the problem of the structuring of nursing practice. The first is that the patient's dependency places him in a vulnerable situation, and second that his situation is such as to make rational judgement difficult for him. He can be, therefore, exposed to technical incompetence and a wide range of irrational and non-rational practices. Also, it is not only that the patient has a need to be helped but that this need is institutionally categorized and, by institutional arrangement, he finds himself in a defined framework in which the kind of help offered is defined. The study reveals that even in an ideal nurse/patient situation, that is, with a competent nurse and a patient who is a rational layman, the patient is ‘at risk’. This may have very important consequences for the structuring of any practitioner/patient situation.