The aim of study was to investigate the pharmacokinetics and distribution of antithymocyte globulin (ATG) in recipients of partially HLA-matched hematopoietic stem cell transplantation. Fifteen patients with hematological disorders were received hematopoietic stem cell transplantation from partially HLA-matched related donor between October 2003 and October 2004 in the Institute of Hematology and People Hospital, Peking University. All patients including 5 cases of AML, 6 cases of CML, 3 cases of ALL, 1 case of AA were consecutively enrolled in the present study after providing written informed consent. Antithymocyte globulin was administered before allogeneic hematopoietic stem cell transplantation at a dose of 2.5 mg/kg daily for 4 consecutive days (total dose of 10 mg/kg) in the conditioning regimen. The concentration of rabbit ATG in the serum of 15 patients was measured using a new enzyme-linked immunoabsorbent assay (ELISA) for the Fc portion of rabbit IgG. The results showed that the washout phase of ATG elimination was analyzed over 0 - 120 days, results were well-fitted by a single exponential decay giving a mean elimination half-life (t(1/2) beta) of 29.67 +/- 2.60 days. A mean value for the apparent volume of distribution of ATG (V) obtained by analysis of data was 0.12 +/- 0.02 L/kg body weight. The serum concentration of ATG increased up to 44.8% at 5 day before transplantation, peak concentration of ATG was 136.0 +/- 10.3 mg/L, its concentration slowly descend at 0 day, fall up to 7.1 +/- 0.06 microg/ml at 90 day after dosing; t(max) 4.8 +/- 0.7 days; According to AIC (Akaike's information criterion), two compartment model of ATG was estimated. It is concluded that the conditioning regimen containing the dosage of 10 mg/kg of ATG is effective and safely in recipients of partially HLA-matched hematopoietic stem cell transplantation. There is no racial difference in the pharmacokinetics of ATG.