Main objective of this study was to determine whether intrauterine infusion of oxytetracycline (OTC) is an appropriate method for the treatment of postpartum endometritis in dairy cows or not. To this end, 280 lactating Holstein cows with clinical signs of endometritis were randomly assigned into three treatment groups and 186 cows were sampled for cytology experiment. In group 1 (n=73) cows were treated with intrauterine infusion of 5 g/cow 10% OTC. In group 2 (n=44), before intrauterine OTC treatment, caudal epidural anesthesia was used to eliminate straining. In group 3 (n=49) after intrauterine infusion of 5g/cow 10% OTC, 100 ml of normal saline was injected to reduce the concentration of OTC and 20 untreated cows were assigned into control group (group 4). Clinical treatment rates were 79.4%, 68.1%, 65.3 %and 50% in OTC, OTC and caudal epidural anesthesia (OTC+CEA), OTC+Serum and control groups, respectively (P>0.05). Cytological treatment rate in each experiment group was significantly higher than the cytological treatment rate in control group in the second examination (P<0.05). To find out OTC residues in milk by high performance liquid chromatography (HPLC) method, milk samples of 6 treated cows from each group were collected randomly 12, 24, 48, 72 and 96 hours after treatment. Maximum amounts of OTC residues were found 72 hours after treatment in all treatment groups. To evaluate the reproductive performance, the researchers compared 280 cows of treatment groups were compared with 1088 cows that were clinically healthy without any signs of clinical endometritis. The reproductive performance of the two groups were not significantly different, except days to first service which was lower in cows without clinical endometritis (P<0.05). According to the cytology study and the presence of antibiotic residues in milk samples at different times, the use of intrauterine OTC for treatment of clinical endometritis seems skeptical.