Enzyme-linked immunosorbent assay(ELISA) of paragonimiasis iloktsuenensis rat sera was performed using crude antigens of Paragonimus iloktsuenensis(PIA), P. westermani (PWA) and Clonorchis sinensis(CSA). Three crude antigens(PIA, PWA, CSA) were prepared to saline homogenated supernatants of whole adult worms. Infected rat sera were obtained biweekly from the albino rats fed 50∼.80 metacercariae of P. iloktsuenensis through gastric catheter. Experimental groups were divided into 4 groups: GI(controls), GII, GIII and GIV according to 1∼7 worms as GII, 10∼19 worms as GIII and 22∼40 worms as GIV, respectively, In ELISA, the mean OD values of each group for the homologous antigen(PIA) were increased significantly compared to the control sera at the 4th week of infection. With the progress of duration of infection, the mean OD values of infected sera of GII & GIV continuously increased up to the 12th week(last week), but in GIII the mean OD value increased until the loth week. No significance was noted among the infection dose groups (GII, GIII and GIV), after the 6th week of infection. Also, the OD values of all infected rats did not show any Proportional relytionships to the number of worms recovered. In brief, the antibody productivity of individual rats were strongly different. The rat sera infected with p. iloktsuenensis cross-reacted with those infected with P. westermani or C. sinensis, as identified by OD values.