Gross and histological findings were obtained on cysts formed in the reproductive organs, particularly in the mesosalpinx, mesovarium, and fimbria, of 144 gilts and 37 sows. Of the 181 gilts and sows, 63 (34.8%) were found to have cysts which totaled 89. The number of cysts totaled 38 for the gilts and 51 for the sows, with relative frequencies of 18.1% and 48.6%, respectively. The total number of cysts and the incidence were greater in the sows than in the gilts. With regard to the location of cysts, the highest incidence was found in the mesosalpinx (59.6%). The incidence of cysts in the mesovarium and fimbria was relatively low, with 16.9% and 23.6%, respectively. Most cysts were spherical or oval in shape, and below 5.9mm in diameter. A pedunculated cyst was also seen. The bilateral, incidence of the cysts was lower than unilateral, although the incidence was approxmately the same between the gilts and the sows. With regard to the sexual cycle, the high incidence of cysts was found in the follicular phase than in the luteal phase. The cysts putting pressure upon the oviduct were classified into 3 types according to the shape of epithelium and lamina propria. In type I the epithelium had ciliated cells and the lamina propria formed folds. I type 2 ciliated cells existed, but no folds were formed. In type 3, neither ciliated cells nor folds were seen, the histological change, including partial atrophy and lack of folds in the tubal mucosa were seen.