The purpose of the study was to evaluate children's perceptions of their participation as research subjects in a minimal risk research study (a methylphenidate population pharmacokinetic study conducted 8 months earlier). We identified 115 children of an original 189, aged 6 to 19 years, who were responding well to regular methylphenidate for attention-deficit hyperactivity disorder. By using a structured format, telephone interviewers unconnected to the original study questioned the children about what it had been like to be a subject in terms of voluntariness, accuracy of informed consent, reasons for participating, and satisfaction with their experience. Children overwhelmingly perceived their involvement as voluntary (89%) and the information about the study as accurately presented (80%), and they reported a high level of satisfaction with their participation (97%). Self-interest was the most frequently reported reason for participation (47%). In a subsample of 25 children, the percentage of agreement of a 1-week test-retest equaled or exceeded 72% for all answers.