The variation in the enzyme activities of human liver usually represents the particular physiological conditions of each individuals. Thus, we investigated the variation in the activities of SOD, HR and LPO of (1) non-exposed workers (56 subjects), and (2) exposed workers to DMF (43 subjects) in synthetic leather process. Serum levels of enzyme activities of exposed workers (AST:$30.26{pm}20.041$U/L, ALT:$32.72{pm}23.393$U/L, GGT:$28.47{pm}18.635$ U/L, ALP:$81.77{pm}34.879$ U/L)were slightly higher than those in nonexposed workers (AST:$24.00{pm}9.441$ U/L, ALT:$23.89{pm}18.305$U/L, GGT:$21.95{pm}17.970$U/L, ALP:$70.84{pm}24.678$U/L), but only the level of ALT was statistically significant (p< 0.05). Serum levels of LDH, TRF and CHOL in non-exposed workers were slightly higher than those of exposed workers. However, they were not statistically significant (p > 0.05). Serum levels of HR and LPO of the exposed workers appeared to be reduced, but not those of the non-exposed workers. The SOD activities of exposed workers were also slightly higher than those of non-exposed workers, but the results were not statistically significant (p > 0.05). The level of HR was increased with age, but the SOD level was not. These results suggest that the intermittent exposure to DMF at time-weighted average (TWA) level (10 ppm/$m^3$) has affected on the activities of enzymes such as AST, ALT, TRF, but not on the generation of HR, activity of SOD. However, if high dose of DMF was used, there would be severe effects for the generation of HR and LPO.