Placebo-trials on HIV-infected pregnant women in developing countries like Thailand and Uganda have provoked recent controversy. Such experiments aim to find a treatment that will cut the rate of vertical transmission more efficiently than existing treatments like zidovudine. This scenario is first stated as generally as possible, before three ethical principles found in the Belmont Report, itself a sharpening of the Helsinki Declaration, are stated. These three principles are the Principle of Utility, the Principle of Autonomy and the Principle of Justice. These are taken as voices of moral imperative. But although each has intuitive appeal, it can be shown that there are possible scenarios in which they give conflicting prescriptions. To achieve consistency, one must be subordinate to the others. The voice of utility is taken as subordinate to those of justice and autonomy and it is shown that given plausible assumptions about the level of poverty and education in the developing country targeted, the experiment is ruled morally wrong in the name of both justice and autonomy. Moreover, it is argued that no justification can be found for the inclusion of a placebo group, when strictly defined. By contrast, a 'no-treatment' control arm might be justified, but only when the demands of autonomy are satisfied, demands that are more stringent than they might appear. A utilitarian defence of the experiment is examined, namely that the would-be participants are in a no-loss situation, and it is shown that this defence is seriously flawed. Finally, it is concluded that there is no justification for amending the Declaration of Helsinki.