The informed consent is an ethical and legal requirement for potential participants to enroll in a study. There is ample of evidence that understanding consent information and enrollment is challenging for participants in clinical trials. On the other hand, the reasoning process behind decision-making in HIV clinical trials remains mostly unexplored. This study aims to examine the decision-making process of people living with HIV currently participating in antiretroviral clinical trials and their understanding of informed consent. We conducted a qualitative socio-constructivist (...) study using semi-structured interviews. Eleven participants were selected by purposive sampling in Argentina until data saturation was reached. A content analysis was performed. The findings highlight the fact that some participants decided to enroll on the spot, while others made the decision a few days later. In all cases, the decision was based on different aspects of trust (in doctors, in the clinical research site, in the clinical trials system) but also on emotions associated with HIV and/or treatment. Moreover, while people living with HIV felt truly informed after the consent dialogue with a researcher, consent forms were unintelligible and unfriendly. The immediacy of patient decision-making has rarely been described before. Enrollment in an HIV clinical trial is mainly a trust-based decision but this does not contradict the ethical values of autonomy, voluntariness, non-manipulation, and non‐exploitation. Thus, trust is a key issue to be included in reshaping professional practices to ensure the integrity of the informed consent process. (shrink)