The treatment of the control group in externally sponsored clinical trials is the issue of one of the most heated debates in international research ethics. The paradigmatic cases are the mother-to-child HIV-transmission trials that took place in 16 developing countries in 1997, where the control group received a placebo while proven treatment was available in industrialized countries. From this circumstance results the controversy as to whether the sponsor and researchers of externally sponsored trials have to supply a treatment that is (...) usually not available in the host country. From the beginning of the debate the controversial level of treatment has been called “standard of care”. However, besides the disagreement about the quality of the care that has to be supplied, there is as yet no widely accepted clear meaning of this concept. This article examines the fundamental ambiguity of the term and its formal function as an ethical criterion including suggestions on its further use. (shrink)