The aim of this study was to compare the plasma cortisol response between the cows after intravaginal insertion of DIB (Dispositivo Intravaginal Bovino) and those after the insertion of CIDR (Controlled Internal Drug Release). Nine ovariectomized cows (four beef and five dairy) were divided into two groups; four cows were inserted with CIDR for 12 days and five cows were treated with DIB for the same period. All the cows did not have any abnormality in the vagina before insertion of the devices. Blood samples were collected via the tail venipuncture once a day at 8:30 to 9:00 for 7 days before treatment and once at 5-10 minutes before insertion, every two hours for 24 hours after the insertion and once daily thereafter until 3 days after removal of the devices. Plasma cortisol concentrations were estimated by an enzyme immunoassay. Mean plasma cortisol concentrations in nine cows for seven days before treatment remained stable. Immediately before the insertion mean of plasma cortisol concentrations in cows treated with CIDR was 3.6 ± 0.6 ng/ml and 2.9 ± 0.7 ng/ml in those treated with DIB. After the insertion, plasma cortisol concentrations increased rapidly (P<0.05), reaching the peak with 8.5 ± 2.5 ng/ml at 4 h (DIB) or 6.4 ± 1.0 ng/ml at 6 h (CIDR) and then gradually decreased to basal levels at 12 h and remained stable thereafter. There was no significant difference in plasma cortisol responses which were marginal and temporal between DIB treated and CIDR treated cows.