This paper examines the concept of a 'standard of care' as it has been used in recent arguments over the ethics of international human-subjects research. It argues that this concept is ambiguous along two different axes, with the result that there are at least four possible standard of care arguments that have not always been clearly distinguished. As a result, it has been difficult to assess the implications of opposing standard of care arguments, to recognize important differences in their supporting rationales, and even to locate the crux of the disagreement in some instances. The goal of the present discussion, therefore, is to disambiguate the concept of a 'standard of care' and to highlight the areas of genuine disagreement among different standards. In the end it is argued that one standard of care argument in particular is more complex than either its proponents or its critics may have recognized and that understanding this possibility opens up a potentially promising avenue of inquiry that remains to be carefully explored.