After parturition, the genital system is returning to its normal non-pregnant state. The reduction in the size of the genital tract is called INVOLUTION. INVOLUTION of the ovine uterus after parturition was investigated following the intrauterine administration of oxytetracycline (2 gr). Under general anaesthesia and using strict asepsis the genital tract of ewes in 2nd month of gestation were exteriorised through a posterior midline laparatomy and four non-toxic split aluminium shots with different sizes were sutured to the wall of the uterine horns and internal os of the cervix (Radio-opaque markers method). Then, for assessment of uterine INVOLUTION sequential radiographs were taken on the day of lambing and 3, 7, 14, 28 and 42 days after parturition. Three measurements (uterine body length, gravid and non-gravid horn diameter) were made on each of the radiographs. INVOLUTION of the uterine body length and gravid horn diameter were completed by about 28 days after parturition in sterile water treated (Control) group (n = 6) whereas completion of the non-gravid horn INVOLUTION was significantly more rapid (by about 14 days after parturition) than gravid horn (P<0.05). The mean of the uterine body length, gravid and non-gravid horn diameter of oxytetracycline administered (treatment) ewes (n = 4) at any stages after parturition were non significantly higher than the control group (P>0.05). The mean of three measurements of the treatment (n = 4) group at the day 42 were similar to the control group at the day 14 after lambing. However, the present study demonstrates that treatment with intrauterine oxytetracycline may prolong INVOLUTION of the reproductive tract of ewes after parturition.