In order to observe the complement fixation test and immuno-diffusion test of paragonimiasis, the sera taken at 10 days intervals up to 150 days from cats infected with Paragonimus westermani were examined by the above two immunological methods.

The resultant findings were as follows:

1) The complement fixation test showed positive reaction 20 days after the infection with 20 metacercariae, and 40-50 days after the infection with 10 metacercariae. The highest titer was observed 110 days later following the acceleration at 80 days later.

2) In immuno-diffusion test, one are appeared 30 days after the infection with 20 metacercariae, but 60 days after the infection with 10 metacercariae. However, more than two arcs were observed since 70 days after infection.

3) A relatively wide band appeared by the antigens of Fresh worm material and Somatic material. But relatively clear precipitin lines were observed in the diffusion test with V.B.S. antigen, increasing to 3-4 arcs after 110days.

4) In general, complement fixation test showed earlier and higher sensitive reaction than immuno-diffusion test, and was considered to be more valuable method forr immunological diagnosis.