A urinary assay (17 kgs/creatinine) was used to measure compliance in 31 acute lymphocytic leukemia patients under 15 years of age receiving oral prednisone. Demographic data and psychological test responses of patients and their parents were correlated with the urinary assays. Results indicated that while the rate of compliance was the same for boys and girls, the psychological correlates were very different. Parental personality traits and attitudes were more involved with boy's compliance than with girl's. Some of the parent variables associated with compliance in boys were hostility, anxiety, and obsessive-compulsive behavior. Parents described compliant boys as vulnerable. These traits usually are considered maladaptive but in this case appear to facilitate boy's compliance. For girls, far fewer parent variables were associated with compliance. Parents seemed to have less worry and concern about their daughters and presumably give them the responsibility for their own medication. It was the girl's own anxiety which predicted compliance.