Abstract: The aim of this study, was to determine the level of some important production characteristics and to investigate some environmental factors affecting fertility traits of purebred Arabian mares raised at Anadolu state farm in Eskisehir for last 30 years. This study was carried out on the data obtained from 2189 mares for fertility traits between 1976 and 2006. The least square means of gestation length, first servicing period, service period, foaling interval, oestrus cycle per pregnancy and NIPC was 334.3±0.22, 24.91±0.93, 45.12±1.09 and 371.79±1.57 days, 1.53±0.03, 5.68±0.10, respectively. Heritability of gestation duration was estimated 0.22±0.06 by paternal half sib method from 2093 gestation duration of purebred Arabian mares sired by 49 stallion, which had at least 5 daughters. It can said that effect of environmental factors on gestation duration is higher than genetic factors. The average gestation length was estimated as 334.3±0.22 days for Arabian mares. Effects of foal sex, breeding age, breeding month and breeding year were significant (p<0.001-0.05). Colt foal pregnancies were longer than fillies. Gestation duration increased with age up to maturity and decreased thereafter. Shortest gestation duration was found in mares bred in June. Although, the effect of breeding month on first servicing period was insignificant (p>0.05), effect of breeding month on service period, on foaling interval, on oestrus cycle per pregnancy and on Number of Insemination for Per Conception (NIPC) was significant (p<0.001). Although, effect of breeding year on oestrus cycle per pregnancy was insignificant (p>0.05), effect of foaling year on first servicing period, on service period, on foaling interval and on NIPC was significant (p<0.001-0.05). On the basis of mares at mating oestrus, from fertility records of 3223 mares, ratios of oestrus, sub-oestrus, pregnancy, sterility, parturition and abortion were 98.70, 1.30, 74.00, 26.00, 69.07 and 4.93% for Arabian mares, respectively. As ratio of parturition was >80% after 2000 year, it can be concluded that reproductive performance of Arabian horses are higher after 2000 year. The factors have the greatest influence over the fertility traits were the breeding month of mares and breeding year. Better performance levels can be obtained by culling old, emphysema pulmonum and infertile mares and better feeding and attention. Oestrus detection and artificial insemination should be performed at the right time and in an appropriate way. An appropriate teasing technique should practice in deciding whether mares are properly in heat. Controls of ovulation and gestation examination by using ultrasonography should be done.