Reproduction in domestic animals, as a major source of food and other products for human, has great importance and study of related subjects including sex differentiation and gonadogenesis during fetal life can solve many questions on normal development and various disorders of urogenital system. Since studies on sex differentiation in goat fetus are scarce, this study was performed. Twenty-five goat fetuses with 5-40 mm crown-rump lengths (CRL) were obtained from slaughterhouse and fixed in

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... formalin solution immediately. The development and features of external genitalia of these fetuses as well as their sex differentiation were then examined. In externally indifferentiated fetuses, the cranial half of the body was cut away at the diaphragmatic level and serial sections, 6-micron thick, were prepared and the ovarian and testicular differentiation was studied. Results showed that considering the development of the external genitalia, external sex differentiation occurs at 31 mm CRL in male fetuses and at 33 mm CRL in female fetuses. Microscopic studies suggested that testicular tissue differentiation occurs at 23 mm CRL with formation of tunica albuginea and medullary cords. Ovarian tissue differentiation occurs at 38 mm CRL with establishment of cortical and medullary regions.