BACKGROUND Doxorubicin cardiotoxicity remains a serious problem in children with malignancy. The present study was undertaken to determine if the administration of consecutive divided daily doses of doxorubicin would significantly reduce the likelihood of cardiotoxicity in children compared with a single dose administration regimen. METHODS One hundred thirteen children (60 boys and 53 girls) received doxorubicin either by single dose infusion or by a consecutive divided daily dose schedule. The divided dose patients received one third of the total cycle dose over 20 minutes for 3 consecutive days. Patients treated according to a single dose schedule received the cycle dose as a 20-minute infusion. The mean doxorubicin dose was 341 mg/m2. Patients were followed up for 4-180 months. There were 60 boys and 53 girls in the series. RESULTS Fifteen patients developed cardiacdysfunction, eight of whom died of progressive cardiac failure. There was no significant difference in the incidence of cardiac dysfunction between the divided and single dose infusion groups. More girls than boys developed cardiac dysfunction and more girls died of progressive cardiac failure; this difference was not statistically significant. The median time to the development of cardiac failure was 2 months. CONCLUSIONS The divided dose regimen did not alter the incidence of cardiotoxicity. Other schedules should therefore be investigated. Our data suggest that, at similar cumulative doses, girls are more likely to develop cardiac dysfunction than are boys. If the sex-related difference is proved in larger series of patients, it may be prudent to lower the recommended cumulative doses for girls.