The objective of this study was to determine the effects of various estrous synchronization protocols utilizing the five-day controlled internal drug releasing (CIDR) inserts that are infused with progesterone (P4) alone and when coupled with gonadotropin-releasing hormone (GnRH) and prostaglandin (PG) during different breeding seasons. Ewes received either 1 of 4 treatments: 1) Untreated (U); 2) 5 d CIDR (0.3 g P4) insert (C); 3) 5 d CIDR and PG at CIDR removal (d 0, P); or 4) GnRH at 5 d CIDR insertion and PG at CIDR removal (G). In Experiment 1, overall days to estrus were greater (P ≤ 0.01) in U and P compared with C. In Experiment 2, overall days to estrus were greater (P ≤ 0.02) in U and P compared with G. In summary, the 5 d CIDR reduces the number of days required to bring ewes into estrus when compared to untreated ewes.