Background. The factors influencing family decisions to participate in adolescent asthma research are not well understood. Legal and ethical imperatives require adolescent research participation to be voluntary. While parents and adolescents often agree about research decisions, disagreements may also occur with relative frequency. Physician recommendations are also known to influence research participation decisions. Little attention has been given to how these dynamics may affect adolescents' involvement in decisions to participate in research. Objective. To examine the influence of family and physician-investigator relationships and recommendations on adolescent asthma clinical research participation decisions. Methods. A statewide community sample of 111 adolescents 11 to 17 years of age, with a diagnosis of asthma, and their parents participated in this study. Adolescents received a medical evaluation from an asthma specialist and then the family was offered participation in a hypothetical asthma clinical trial. By random assignment, the research study was presented by either the same or an unknown asthma specialist, and half the families in each group also received affirmative recommendations from the asthma specialist to participate in the hypothetical asthma clinical trial. Parents and adolescents made initial private decisions about participating in the trial. Then, following a family discussion of the clinical trial, a final research participation decision was made. Results. Thirty-three percent of parents and adolescents initially disagreed about the research participation decision. When disagreements occurred, final decisions followed the parents' initial views except when the physician-investigator was known and a recommendation was made. Families with initial disagreement about participating were less likely to enroll when the investigator was unknown or when no recommendation was made. Adolescents who initially disagreed with parents' views were less likely to concur with the final research participation decision, felt less comfortable, and were less likely to feel they influenced the decision. Conclusions. Parents' views on research decisions take precedence over adolescents' views in most circumstances. Physician-investigator relationships may reduce parental resistance to participation and enhance adolescent decision-making autonomy when research participation is desired by the adolescent.