In this study, the partitioning of beta-amylase in aqueous two-phase systems (ATPS) containing polyethylene glycol (PEG) with a molar mass of 6000 and 10 000 and KH(2)PO(4) at T = (301.65 and 304.65) K was experimentally studied. In addition, the partitioning of amyloglucosidase in ATPS containing polyethylene glycol with molar mass of 4000, 6000, and 10 000 in the presence of Na(2)SO(4) at T = (301.65 and 305.65) K was investigated. The effects of molar mass of PEG, temperature, mass fractions of salt, and the length of the tie line on partition coefficients of the enzymes were also studied. The experimental results showed that while the partition coefficients of enzymes decrease with increasing molar mass of polymer they increase with increasing tie line length as well as system temperature. Also, the salt concentrations in ATPS can significantly affect the partitioning of enzymes between the top and bottom phases. It was concluded that the partition coefficients of enzymes increase with an increase in the salt concentrations. The experimental data of the partition coefficients were correlated with the equation proposed by Diamond and Hsu. The results indicated that the Diamond and Hsu equation which is based on the lattice theory of Flory-Huggins can accurately correlate the experimental data collected in this work.