Abstract： Objective To study relationship between daunorubicin (DNR) pharmacokinetics and efficacy and toxicity in children with acute leukemia.Methods (1) The concentration of DNR in plasma of children with acute leukemia was determined by high performance liquid chromatography (HPLC)-fluorescence detection method.Plasma was sampled frequently from the start of the infusion till the end of 24 h.DNR pharmacokinetics was studied by determination of the concentrations.(2) Efficacy and toxicity were monitored in each period after chemotherapy.Laboratory studies included examination of bone marrow,white blood cell count,electrocardiogram,echocardiogram,myocardial enzymogram,the liver and kidney function.Results (1) DNR was eliminated from plasma in a two-compartment manner.The maximum concentration was seen 1-3 h after infusion.Cmax was 63.50 ug/L.Tmax was 1.45 h.The concentration decreased quickly to a low level of about 11.52 ug/L from the end of 2 hours infusion.There was a large inter-individual difference in pharmacokinetic parameters of DNR.The difference of CL was 9-fold,AUC and that of children younger than 6 years was 1.8 h(P<0.05);Cmax of children older than 6 years was 90.77 ug/L,younger than 6 years was 57.44 ug/L(P<0.05).Conclusion (1) There is a large inter-individual difference in pharmacokinetic parameters of DNR in children.It may predict individual variety of efficacy and toxicity.Therapeutic drug monitoring is important.(2) Male patients and children older than 6 years had a higher bioavailability and lower metabolism,toxicity may easily occur in such children,therefore they may need lower dose.