Abstract Tropical cow-calf operations using Bos indicus crossbreds are characterized by extended periods of time before the establishment of ovarian cyclicity. The aim was to determine whether the increase of progesterone concentrations during postpartum anestrous using intravaginal devices along with injection of estradiol benzoate would advance the occurrence of first ovulation after calving. 269 suckled crossbred cows kept in different farms at North-Santander (Colombia) were randomized in one of the following treatments: 1:Control (n = 88) no further treatment; 2:P4 (n = 91) cows received an intravaginal device containing 0.588 g of progesterone during 7 days at day 50±3 after calving; 3:P4+E2 (n = 90) as treatment 2 plus an additional injection of 2.0 mg of estradiol benzoate at the time of device insertion. Ovarian ultrasound was performed weekly starting on the day of treatments until ovulation (disappearance of a dominant follicle with later appearance of a corpus luteum within two consecutive examinations). Calving-Ovulation Interval was recorded and means between groups were analyzed using ANOVA (α=0.05). For the control group, COI tended (P = 0.08) to be longer for primiparous cows (149.6±4.5 days, n = 14) compared to multiparous cows (140.4±2.1d, n = 74). Treatment with P4 reduced the COI for both primiparous (105.3±5.4d, n = 15; P < 0.0001) and multiparous (96.4±3.0d, n = 76; P < 0.0001) compared to the controls (P = 0.21 between groups of age). When primiparous cows were treated with P4+E2 the COI decreased compared to both P4 and control treatments (82.3±2.8d, n = 17; P < 0.0001). However, in multiparous cows there was no effect of P4+E2 compared to P4 treatment (94.6±2.6d, n = 73; P = 0.65), then COI was shorter for primiparous compared to multiparous cows (P = 0.03) with P4+E2 treatment. The use of an intravaginal device containing progesterone advances the time of first ovulation after calving in suckled cows. Additional use of estradiol benzoate reduces the time for first ovulation in primiparous but not multiparous cows.