摘要SET is a multifunctional protein involved in regulating many biological processes of the cell cycle. It is also a regulator of steroidogenesis in the ovary. However, the expression of SET protein in testis, and its function, still remains ambiguous. In this study, we observed the expression of SET in the testes of mice at different developmental stages, and have discussed its potential function in regulating spermatogenesis and androgen production. Forty?eight male mice at different developmental stages(1week old as the infancy group; 4weeks old as the prepubertal group; 12weeks old as the adult group; over12months old as the ageing group) were used. Cellular location of SET protein in the testes was observed by immuno?histochemistry. Expression levels of Set mRNA and SET protein were analyzed by quantitative polymerase chain reaction and Western blotting. SET protein was expressed in spermatogonial cells and spermatocytes; the highest level was mainly in haploid and tetraploid cells of the prepubertal and adult groups, and Leydig cells of the adult and ageing groups. There was a low expression in Sertoli cells. Expression of Set mRNA in the prepubertal group was signiifcantly higher than that in the adult group(P<0.05), while expression of SET protein was at the highest level in the adult group(P<0.05).SET protein is mainly expressed in spermatogonial cells and spermatocytes, and poorly expressed in Sertoli cells, suggesting that it is involved in spermatogenesis. Expression of SET protein in Leydig cells suggests a possible role in steroidogenesis.