Our objective was to characterize ovarian dynamics in lactating dairy cows diagnosed nonpregnant after AI focusing on time points when resynchronization programs are initiated or PGF2α can be used to induce estrus expression. After synchronization with the Presynch-Ovsynch (PGF-14d-PGF-12d-GnRH-7d-PGF56h-GnRH-16h-TAI) protocol cows (n = 64) received timed-AI. Blood was collected every 48 h from 14 to 42 d after AI to determine concentrations of progesterone (P4) and estradiol (E2). Daily, ovarian ultrasound (US) was used to determine size and location of all ovarian structures. Retrospectively, cows were classified as pregnant (n = 25; PG) when a viable embryo was observed (excluded from analysis) or nonpregnant (n = 39; NP) when no viable embryo was observed. A cow was considered to have an active CL (ACL) when P4 > 1 ng/mL and ≥ 1 CL was observed. Also, a CL was considered mature (MCL) starting 7 d after ovulation based on the timing when the CL becomes sensitive to PGF2α. Follicles were considered active (AFOL) when reached 10 mm until 2 consecutive days of reduction in diameter. Periods evaluated were: 24(D24), 32(D32), and 38(D38) d after AI. Parameters evaluated were cows with ACL, MCL, and an AFOL by day, E2 concentrations and E2 to P4 ratio. Quantitative data were analyzed by ANOVA using PROC MIXED whereas binary data were analyzed by logistical regression using PROC GLIMMIX of SAS. More (P < 0.01) cows had an ACL on D32 (82.1%) and D38 (84.2%) than on D24 (35.9%). The greatest (P < 0.01) proportion of cows with a MCL was for D38 (84.6%) followed by D32 (56.4%) and least for D24 (28.2%). The proportion of cows with an AFOL tended (P = 0.06) to be affected by day with 79.5, 92.3, and 97.4% of cows with an AFOL for D24, D32, and D38, respectively. Concentrations of E2 were greater (P = 0.05) for cows with an AFOL (1.1 ± 0.3 pg/mL) vs cows without AFOL (0.5 ± 0.1 pg/mL) across all days. Concentrations of E2 were affected by day because on D24 (1.3 ± 0.2 pg/mL) E2 was greater (P < 0.05) than for D32 (0.7 ± 0.2 pg/mL) whereas on D38 (1.0 ± 0.2 pg/mL) E2 was intermediate. We conclude that there is more variation in ovarian function than expected based on the number of days after AI in nonpregnant previously inseminated cows. Supported by Hatch project NYC-127813.