Gynecological examination is essential to assess the reproductive tract of mares and can provide important information about the uterine environment. It includes physical, vaginal, and rectal examination, ultrasound, cytology, culture, and endometrial biopsy. The present study aimed to perform gynecological examination and fertility to assess the fertility prognosis of Pantaneiro mares that have not been reproductively active and to determine their reproductive ability. Eight mares underwent ultrasound and gynecological examination and artificial insemination. Ultrasound revealed changes only in one mare. Histopathological findings were mild, such as periglandular and perivascular inflammatory cell infiltrates, fibrotic areas, glandular dilation, glandular island formation, and edema due to the phase of the estrous cycle. One animal was classified in category I and the others in category IIA. Cytological changes were found in only one mare. Endometrial culture from five mares resulted in isolation of Pseudomonas sp., Bacillus sp., Escherichia coli and Candida sp. Only four mares resulted pregnant through artificial insemination, using the same stallion with fresh semen, which has been proving fertility. Thus, mares with better uterine conditions will not always become pregnant and those with mild changes will not always be barren.