The KyoT expression in the adult mouse was reported here for further investigation on the functions of KyoT in adult mouse. To study the expression of mRNA and protein of KyoT, Northern blot, RT-PCR, Immunohistochemical SABC methods and in situ hybridization methods were used in the experiments. Two kinds of KyoT were expressed at high levels in testis of adult mouse, and KyoT immunore activity was mainly located in Leydig's cells. The reactive substance was distributed in cytoplasm rather than in nuclei. KyoT mRNA hybridization signals were also detected in cytoplasm of Leydig's cells rather than in nuclei. The spermatogenic cells and negative controls showed negative results. These results suggest that KyoT was expressed in testis of adult mouse and mainly located in Leydig's cells.