We classified the estrous cycle of the Mongolian gerbil and described the structures and relations of the uterine tube in the pelvic abdominal cavity and the histology of its coating epithelium. From 19 adult female Mongolian gerbils the uterine tube has been investigated by anatomy and histology using intact tissue. A polyestrous and irregular cycle was observed, with five different phases: proestrus, estrus I, estrus II, metaestrus, and diestrus. Estrus I is characterized by a smaller number of dispersed keratinized cells compared to estrus II. The uterine tube is related to the distal extremity of the uterine horn and to the ovary and presents an outer serosal covering (peritoneal visceral lamina), a muscular tunica media consisting of smooth circular fibers and a mucosal layer with simple covering epithelium composed of secretory and ciliated cylindric cells. Histologically, it is divided into four different areas: intramural, isthmus, ampulla and infundibulum. The gerbil is not an ideal model for the study of the estrous cycle due to its irregularity. The anatomy and histology of the uterine tube is similar to that of rodents used as laboratory animals