Aim: To study the effect of prenatal exposure to diethylstilbestrol (DES) and the role of actin and proliferating cell nuclear antigen (PCNA) on testicular gubernaculum development in fetal male Kunming mice. Methods: Pregnant mice were randomly assigned to 6 groups and injected with DES subcutaneously from gestational day 9 (E9) to day 17 (E17) at doses of 0, 25, 50, 100, 200 μg·kg-1·d-1 in 0.2 mL dimethyl sulfoxide (DMSO). On E17 they were sacrificed and fetuses quickly removed for fixation. Male fetuses were sliced on serial coronal plane. Histologi-cal changes were observed under the light microscope (LM) and ultrastructural changes with the scanning and transmission electron microscopes (SEM & TEM). The expression intensity of actin and PCNA in the gubernacula was quantitated by immunohistochemistry. Results: The mortality of the fetuses was higher in the DES-treated groups than that in the DMSO and saline controls (P<0.05). Under LM the gubernacula were seen to be poorly developed with smaller b Aim: To study the effect of prenatal exposure to diethylstilbestrol (DES) and the role of actin and proliferating cell nuclear antigen (PCNA) on testicular gubernaculum development in fetal male Kunming mice. Methods: Pregnant mice were randomly assigned to 6 groups and injected with DES subcutaneously from gestational day 9 (E9) to day 17 (E17) at doses of 0, 25, 50, 100, 200 μg · kg -1 · d -1 in 0.2 mL dimethyl sulfoxide (DMSO) and fetuses quickly removed for fixation. Male fetuses were sliced ​​on serial coronal plane. Histologi-cal changes were observed under the light microscope (LM) and ultrastructural changes with the scanning and transmission electron microscopes (SEM & TEM). The expression intensity of actin and PCNA in the gubernacula was quantitated by immunohistochemistry. Results: The mortality of the fetuses was higher in the DES-treated groups than that in the DMSO and saline controls (P <0.05). Under LM the gubernacula were seen to be poorly devel oped with smaller b