Albumin has been widely served as nutrients for tissue cultures in laboratory field and as plasma expander for blood transfusion in clinical field. Recently, human serum albumin (HSA) is sometime used as supporting materials in medium for human ES and iPS cell culture. In respect of thiol group of the protein, HSA has one highly reactive thiol group at position 34 (Cys-34). When it is a free state, it is called human mercaptalbumin (HMA, reduced form). On the other hand, when the thiol group is modified by oxidation, it is called human non-mercaptalbumin (HNA, oxidized form). HNA is further classified into two forms; HNA-1, mixed disulfide with cysteine; HNA-2, more higher oxidation products. Therefore, HSA in the exracellular fluids (ECF) is a mixture of HMA and HNA, i.e., a protein redox couple in ECF. As a commercially available HSA product is manufactured from large-scale pooled blood, the serum-derived albumin may have a different degree on thiol-redox state and protein carbonylation. By using a convenient HPLC system for the clear separation from HSA to HMA, HNA-1 and HNA-2, we examined the redox state of HSA products from various sources. Protein carbonylation is analyzed by Protein Carbonyl Assay Kit (Cayman Chem. Co.). All HSA products were obtained from Sigma Co. (product No. A1653 (5 lots), A3782 (5 lots) and A9731 (2 lots)). The A1653 is a product corresponding to Cohn Fraction V from serum-derived albumin, which is a starting material from pooled sera. The A3782 is a final product, which is prepared from A1653 through lyophilized and defatted processes. On the other hand, the A9731 is a recombinant HSA product expressed in rice (Cellastim®). Mean HMA values for A1653, A3782 and A9731 were 29.3. 28.2 and 33.1%, respectively. Mean values for carbonyl content of those products were 10.5, 18.7 and 31.4 nmol/mg protein, respectively. In order to evaluate the possible role of HSA as growth-promoting potential for cell culture in vitro, A1653 (lot 030M7034V), A3782 (lot 090M7001V) and A9731 (lot 061M1563) were used for U937 cells. For cell growth response, the ability of A9731 (recombinant albumin) was stronger than those of A1653 and A3782 (serum-derived albumin). These results suggest that the heterogeneity of thiol-redox state and protein carbonylation of various kinds of commercial HSA products appears to occur during manufacturing process of HSA from large-scale pooled blood. However, a recombinant albumin may have a different manner from that of a serum-derived albumin. This is especially important in studies where these products are used to interact with other biological materials in both laboratory and clinical fields.