Informed parental permission is required for a child to participate in research. While parents receive information concerning the research via written documentation and/or verbal interaction with researchers, the extent to which parents understand the research aims and procedures has not been widely studied. The current study assessed the extent of parental research knowledge among 95 parents whose children were involved in an 8-week placebo-controlled randomized trial of risperidone in autism; participants completed a questionnaire probing knowledge of the research aims and procedures following the study. Results indicated consistently high levels of research knowledge among the sample: 99 percent knew of possible placebo assignment, 96 to 98 percent knew of potential risks and benefits, and 90 to 95 percent knew of the main side effects. However, only 72 percent of parents were aware that the assignment to treatment or placebo was random, believing instead that assignment was based on individual need. The findings suggest the need for researchers to clarify the meaning of randomization when explaining research procedures. Table, references