The GnRH agonist, Lecirelin (Gestran Plus®; ARSA S.R.L., Buenos Aires, Argentina), was tested for the ability to induce and synchronize ovulation in sows. Sows were uniformly allocated in two groups (n = 56, each) according to parity (2-6), weaning to estrus interval (WEI) and body condition score (BCS). The GnRH analog (25 µg, 1 ml) and saline solution (control group) were injected at estrus onset. Estrus detection and transcutaneous real-time ultrasonography were performed every 8 h. Duration of estrus for the control and treated groups was 66.3 ± 1.3 h and 61.3 ± 1.3 h (P < 0.007), respectively. Interval from estrus onset to ovulation (IEO) was 44.3 ± 1.2 h and 39.9 ± 1.2 h (P < 0.012) for the control and treated groups, respectively. Up to 40 h after treatment administration, 70.9% of Lecirelin sows had ovulated whereas 48.2% of control sows ovulated in the same period (P < 0.01). There was a tendency for a greater proportion of Lecirelin sows (92.7%) to ovulate during the 48-h period post treatment compared to control sows (82.4%). Reproductive performance (farrowing rate, number of total piglets born, piglets born alive, stillborn piglets and mummified fetuses) was not affected (P > 0.05) by induction of ovulation with Lecirelin. Based on the results found, it can be concluded that Lecirelin injection at estrus onset reduces estrus length and interval between estrus onset and ovulation with no influence on the subsequent reproductive performance.