Abstract: In the present study, the kinetic change of IHA antibody responses in rats infected with Paragonimus westermani was observed before and after pyquiton treatment. It was found that antibody tilers against both metacercaria and adult worm antigens were distinctly increased shortly after an effective treatment with peaks appearing both around the 10th day post-treatment. They began to decline thereafter and reached relatively low levels at the 120th and 90th day respectively. In unsuitable rat hosts, the anti-metacercaria antibodies, rather than the anti-adult antibodies and vice versa in suitable dog hosts, were shown to have increased to a higher level after treatment and maintained for a longer period, these results further confirmed that the antibody responses in Paragonsmus westermani-infected hosts were stage-specific.