Objective: To explore parents' attitudes to children's participation in randomized controlled trials. Study design: Qualitative analysis of focus group discussions involving 33 parents from a pediatric teaching hospital and local school in Australia. Parents varied in age, gender, ethnicity, level of education, research experience, and child's health status. The transcribed discussions were analyzed by theme linkage using the constant comparative method. Results: Parents balance risks and benefits when deciding about trial participation for their child. Perceived benefits include the offer of hope, better care of their child, the opportunity to access new treatments, healthcare professionals and health information, meeting others in similar circumstances, and helping others. Perceived risks include potential side effects, being randomized to ineffective treatments, and the inconvenience of participation. The decision for trial participation is also influenced by parental factors (parents' knowledge, beliefs, and emotional responses), child factors (the child's health status and preference about participation), trial factors (the use of placebos and uncertainties of participation), and doctor factors (doctor's recommendations and communication of trial information). Conclusions: Educating parents about trials, improving communication between trialists, pediatricians, and parents, increasing incentives while decreasing inconveniences, and providing decision aids for parents may increase parents' willingness to participate in trials.