Abstract: A total of 19 female adult filarite containing microfilarke in uteri collected from 25 filariasis patients were examined. Light transmission microscopic observations showed: (1) some of the adult worms entered the lumen of blood vessels by penetrating the venous wall and discharged immature and mature microfilariae and embryos into the blood stream; (2) microfilariae developed into maturation in the uterus of adult female worms, but when the adult worm began to degenerate, the microfilariae did not degenerate concurrently; (3) some microfilariae could form thrombus, inducing the infiltration of segmented neutrophils and eosinophils followed by the formation of granuloma; (4) embryos 8 female adults parasitizing lymphatics were seen to discharge immature microfilariae and ova, which might form emboli after entering the blood stream.