The experiment was designed to evaluate timing of GnRH administration in beef cows based on estrous status with split-time AI. Estrus was synchronized in 622 cows across 6 locations by using the 7-d CO-Synch + CIDR protocol (100 μg GnRH + CIDR insert [1.38 g progesterone] on d 0; 25 mg PGF_2α [PG] at CIDR removal on d 7; and 100 μg GnRH depending on treatment). Estrous detection aids (Estrotect) were applied at CIDR removal and PG on d 7, with estrus recorded at 66 and 90 h after PG on d 10 and 11, respectively. Treatments were balanced across locations; cows within location were randomly assigned to one of 2 treatments based on age, BCS, and days postpartum. Timing of AI was based on expression of estrus 66 h after PG. Cows in each treatment that exhibited estrus by 66 h were inseminated; whereas AI was delayed 24 h until 90 h after PG for cows failing to exhibit estrus by 66 h. Cows in treatment 1 were administered GnRH 66 h after PG irrespective of estrus expression; whereas in treatment 2, cows were administered GnRH coincident with delayed AI only if not detected in estrus at 66 h after PG. Data were analyzed using PROC FREQ in SAS. Treatment affected overall estrous response (1 = 85%; 2 = 90%; P = 0.04) but did not affect total AI pregnancy rate (1 = 58%; 2 = 57%; P = 0.89). There were no differences between treatments in estrous response at 66 h (1 = 73%; 2 = 75%; P = 0.47); and pregnancy rate resulting from AI for cows inseminated at 66 h was not influenced by GnRH (1 = 63%; 2 = 59%; P = 0.50). Estrous response during the 24 h delay period differed between treatments (1 = 45%; 2 = 61% P = 0.04), although AI pregnancy rate for cows inseminated at 90 h did not differ (1 = 44%; 2 = 49%; P = 0.51). In summary, when split-time AI is used in conjunction with the 7 d CO-Synch + CIDR protocol, administration of GnRH at AI to cows that exhibit estrus by 66 h after PG is not warranted. These data indicate that delayed administration of GnRH to 90 h coincident with AI among cows failing to exhibit estrus by 66 h after PG results in a greater overall estrous response.