This experiment was carried out to study the effect of the rat and bull spermatozoa motility on the transport and leucocytic response in the genital tract o the estrous rat. Further study was also made to investigate the effect of the etsrogen and progesterone on the infiltration of leucocyte in the ovariectomized rat. Each rat was injected with motile, nonmotile rat or motile bull spermatozoa into the lower part of the right uterine horn of the normal estrous rat after laparotomy and motile rat spermatozoa to they hormone-treated rat. In this study 60 mature female albino rats were used. Time of heat was determined by vaginal smear and then confirmed by vasoectomized male. At 1, 8 or 16 hrs. after injection of the semen, the number of spermatozoa and leucocytes in various segments of the tract was counted and compared with each treatment. The results obtained were as follows: 1) The distribution of spermatozoa in the right uterus at 1 hr. after injection was not significantly different among the three treatments and the segments investigated, but more spermatozoa were found in Lower part than upper part at 8 hrs. in all treatments (P$lt;0.05). At 8 and 16 hrs. the number of spermatozoa was diminished greatly more than hr., which w-as caused by evacuation of the uterine contents into the vagina. The number of evacuated spermatozoa into the vaging was significantly appeared at 8 hrs. as compared with I hr. or 16 hrs. (P$lt;0.05). 2) The total number of spermatozoa reached in the righi Fallopian tube was recovered much more in motile rat spermatozoa than the others and showed also in the ampulla, site of fertilization. Even though the small number of spermatozoa was recovered is the Fallopian tube, the nonmotile rat and motile bull spermatozoa can pass through the utero-tubal junction. However, it was not utterly found in the site of fertilization. 3) The leucocytic response in normal estrous rat was not significantly affected by spermatozoan motility of the rat and bulk. The number of leacocytes in various segments of the genital tract was statistcally significant less in the vagina than sipper part and lower part of the uterus (P$lt;0.01 and P$lt;0.05, resp.), but no significant difference was found between upper and lower part. The difference of leucocytic response was not observed significantly between 8 and 16 hrs., but highly significant difference was observed between 1 hr. and the others. 4) In the ovarian hormone-treated rat after ovariectomy, the leucocytic response was observed significantly different among the treatments (P$lt;0.05) and the intervals investigated(P$lt;0.01). At 1 hr. after injection the difference in the leucocyte number was not significant among the three treatments, but at 8 hrs. (P$lt;0.05) and 16 hrs. (P$lt;0.01) the number of spermatozoa in the progesterone-treated rat was observed significantly less than in the other rat and there were no significant difference among the intervals. However, in the estrogen-treated rat the more spermaozoa were appeared in the genital tract as the time passed after injection.