Objective: Parental permission is required for child research, but parents' understanding of research aims and procedures has not been well documented. Parental research knowledge was assessed during a clinical trial in autism. Method: Parents of 101 children (age 5-17 years) with autism participating in a placebo-controlled trial of risperidone were given a questionnaire at the end of the study. Results: Of the 95 parents completing the questionnaire, 99% knew of possible placebo assignment and that testing the medication efficacy was the main purpose of the investigators; 96% to 98% knew that research involved both risks and potential benefits, identified the study medication, and knew of their right to withdraw at any time; 90% to 95% knew of the medication's main side effects; 87% reported having been informed of possible alternatives to research participation; and 72% were aware that treatment was randomly assigned (whereas 27% reported that treatment was chosen based on individual needs to ensure best care). Parents with a college degree were more likely to recognize the random nature of treatment assignment. Conclusions: Overall, parents were highly knowledgeable of the main research components. About one fourth, however, seemed unaware that treatment was randomly determined and not personalized, suggesting that therapeutic misconception may affect some otherwise well-informed parents. J. Am. Acad. Child Adolesc. Psychiatry, 2005;44(2):145-149. Key Words: ethics, clinical trials.