Fathers of chronically ill children are not well represented in the literature, and we know even less about fathers whose children are involved in clinical research. This study explores the meanings of research and reasons for participation among 12 fathers whose children were engaged in clinical cancer research. Findings revealed two general meanings of the research: the contribution of data and the effect of the intervention on the body of the child. These meanings reflected the research design of survey and experimental or randomized controlled clinical trials, respectively. The possibility of improvement was the reason given for participating in experimental studies, whereas altruism was the reason more likely given unequivocally for survey research. The findings point to two issues inherent to the practice of medical research: the tension between the welfare of the individual and the welfare of the group and the constantly shifting boundaries between acceptable therapy and research.