The purpose of this study was to test the hypotheses that children who receive systematic psychologic preparation and continued supportive care, in contrast to those who do not, would show less upset behavior and more cooperation in the hospital and fewer post-hospital adjustment problems and that their parents would be less anxious and more satisfied with information and care received. Eighty children scheduled for minor surgery and their parents were randomly assigned to experimental and control conditions. The experimental intervention consisted of accurate information about sequences of events, sensory experiences, role expectations and appropriate responses, previews of procedures through play techniques, and supportive care given at critical points pre- and postoperatively. Significant differences between experimental and control children and parents on ratings of upset behavior, cooperation with procedures, pulse before and after painful procedures, resistance to induction, time to first voiding, posthospital adjustment, and parental anxiety and satisfaction with information and care consistently supported the hypotheses. Results were also analyzed in relation to the age and sex of the children and whether parents roomed with the children.