This study was performed with three-hundred and fifteen mares; 110 of them were used as the examination group and 205 of them served as control. The mares in the examination group were regularly inspected and gynecologic and ultrasonographic examinations were done. In suspected cases, swab samples were taken from clitorises and / or uteries ; and biopsy samples were taken from uteri if necessary. Control group was examined only to monitor pregnancy and foaling rates. According to the clinical examination, various clinical findings were observed in 63 of 110 (57 %) mares in the examination group. Sixty three mares were examined microbiologically, 59 mares were examined cytologically and 16 mares were investigated histologically. A total of 144 microorganisms belonging to various genera and species were isolated from 56 of 63 (89 %) mares in microbiological investigation. 43 of 59 (73 %) cytologically and / or histopathologically investigated mares were found positive with regard to uterus disease and 16 (27 %) of them were found negative. Infectious cases were treated with antibiotics or antifungal drugs; chirurgical or hormonal treatment were applied in other pathological cases. The mares in the examination and control groups were compared according to their fertility parameters. The foaling rates were significantly different (74 % and 38 %) in examination and control groups, respectively.