The article presents an ethical analysis of randomized placebo-controlled trials (PCTs) conducted in developing countries in situations where effective treatment already exists elsewhere in the world. The authors examine a fundamental contradiction: the use of a placebo often becomes feasible only because of global inequality in access to healthcare, whereby the actual standard of care for the local population is the complete absence of treatment. Through two case studies: trials of drugs for HIV prevention and for the treatment of infant respiratory distress syndrome (IRDS) —  the ambiguity of ethical evaluation is demonstrated. The key criterion for the acceptability of a PCT is identified as the degree of potential harm: while in the case of HIV the risk to participants was high but not fatal, in the case of IRDS the use of a placebo directly endangered the lives of infants. To provide a philosophical foundation for the problem, the authors employ John Rawls’ thought experiment of the “veil of ignorance” and Gerald Cohen’s test of interpersonal justifiability. From Rawls’ perspective, PCTs perpetuate injustice, because the standard of care cannot depend on a patient’s place of residence, and no one would agree to risk their life due to the contingency of being born in a poor country. Cohen’s test reveals the moral deficiency in the pharmaceutical companies’ reasoning: they themselves contribute to the inaccessibility of medicines and then use this as a justification for placebo controls. The conclusions argue for the necessity of a differentiated approach: prohibition of PCTs when lethal risks are involved, and permissibility only under the condition that the research is aimed at developing accessible treatment for the same vulnerable population.