Altruism is a well-established reason underlying research participation. Less is known about altruism in adolescent-parent decision-making about clinical trials enrolling healthy adolescents. This qualitative investigation focused on identifying spontaneous statements of altruism within adolescent-parent (dyadic) discussions of participation in a hypothetical phase I clinical trial related to adolescent sexual health. Content analysis revealed several response patterns to each other’s altruistic reasoning. Across 70 adolescent-parent dyads in which adolescents were 14 to 17 years of age and 91% of their parents were (...) mothers, a majority (61%) of dyadic discussions included a statement reflecting altruism. Parents responded to adolescents’ statements of altruism more frequently than adolescents responded to parents’ statements. Responses included: expresses concern, reiterates altruistic reasoning, agrees with altruistic reasoning, and adds to/expands altruistic reasoning. Since an altruistic perspective was often balanced with concerns about risk or study procedures, researchers cannot assume that altruism will directly lead to study participation. Optimizing the informed consent process for early phase clinical trials involving healthy adolescents may include supporting parents to have conversations with their adolescents which will enhance their capacity to consider all aspects of trial participation. (shrink)