The aim of this study was to compare effectiveness of antibiotic administration to intravaginal sponge before sponge insertion and investigate duration of sponge treatment for determining changes in the vaginal bacterial flora and fertility parameters. Intravaginal sponges impregnated with 30 mg FGA were inserted in 30 Awassi ewes for long-term (14 days; LT), long-term with antibiotic added sponges (LT-A) and short-term (7 days; ST) during the non-breeding season. All ewes received 400 IU PMSG at sponge withdrawal. Bacterial counts were performed on the vaginal flora samples obtained before the introduction of the sponges, at sponge withdrawal and day of estrous in the treatment groups. The mean value for the colony forming units (x 10(3) mL(-1)) were 5.31, 2.92 and 4.91 on the day of intravaginal sponge insertion and increased to 163.97, 68.34 and 147.0 (p0.05). It was concluded that intravaginal sponge treatments increased bacterial counts, but this increase returned normal values at estrous time. Changes in the number of vaginal flora were not different statistically in the antibiotic added and not added sponge treatment groups at sponge withdrawal and estrous time. Antibiotic administrations to sponge prevented bacterial growth by fist days of sponge treatment. However, this did not affect bacterial count and reproductive response on the day of estrous.