Abstract: In order to verify the estrus activity of the Karayaka ewes reared under natural conditions of the Black Sea Region of Turkey throughout year, ten, 3 years-old Karayaka ewes with an average weight of 46±7.9 kg and with two lambing record, were used. In this experiment four climatic seasons were considered; winter, spring, summer and autumn. Behavioral oestrus was monitored twice a day (7: 00 and 15: 00) during all the experiment by using two teasers rams. The oestrus cycles were quantified within each season and classified as short (≤14 days), normal (15-20 days) and long (or anoestrus, ≥21 days). The percentage of ewes in oestrus was higher (p<0.05) in the autumn than in the winter and summer seasons and the percentage never exceeded 40% in each season. The minimum length of short cycle was 11 days while maximum length of anoestrus was 87 days and the average length of normal cycle was 17.3±1.06. During the experiment, there were 11.9% short cycles, 35.8% normal cycles and 52.3% anoestrus. The percentages of abnormal cycles (short and anoestrus), in relation to total cycles monitored in each season were 87.4, 88.5, 90.9 and 35.5% for winter, spring, summer and autumn, respectively. It can be concluded that Karayaka ewes maintained on rangeland show a low seasonality for oestrus behavior. Thus, in this oestrus pattern, mating may occur from late spring through to late autumn taking into account demands for slaughter lambs and/or feeding of lambs in rangeland.