Phase I-II trials are developing in Pediatrics and raise many complex relational, psychological and ethical issues. We present and discuss these based on an interview in a pediatric oncology setting, with a mother who accepted that her daughter be included in such trials and who expressed why she accepted with great sensitivity and profoundness. She explained that after many years of inefficient treatments she had lost all her landmarks and was ready to accept any proposition, even those she would have considered unacceptable earlier. She did not know whether there is a limit to what is acceptable. Her only objective was to gain any time possible in order to continue living with her daughter. She found it important that the research doctor be different from the doctor involved in patient care, and that the latter remains the major decision-maker and correspondent: thus the child's best interests take precedence over that of research. Interviews with the psycho-oncologist can help the parents and the doctors gain a better insight into the various aspects, rational and irrational, conscious and unconscious, involved in the proposition to participate in a clinical trial and in the parents' or the child's acceptance or refusal.