Estrus synchronization and suitable resynchronization intervention is crucial part of improved reproductive management in dairy industry. Our objectives were to appraise CIDR-EB based estrus synchronization and used CIDR-Ovsynch based resynch protocol in lactating Holstein cows at two different geographical locations. On location A, 160 postpartum cows were enrolled in standard CIDR-EB protocol. Cows were subjected to timed AI and randomly assigned into two groups: 1) control (n=70), subjected to AI on detected estrus (AIDE) from d18-d30 post TAI. Pregnancy rate was diagnosed on d30, d60 and d90 post TAI, 2) resynch (n=90) received CIDR from d14-d21 post TAI. On day 23, all cows received GnRH shot and open cows received remaining Ovsynch protocol. Blood was collected on d14,d16 and d30 for P4 profile. Cross-sectional area of luteal tissue was measured on d30 in pregnant animals in both groups. In experiment II, both control (n=64) and resynch (n=54) groups were similarly treated as in experiment I, without P4 profile and luteal cross-sectional area measurement. Pregnancy rate(PR) was compared by PROC FREQ of SAS. Effect of treatment on circulatory P4 profile and luteal tissue cross-sectional area were analyzed using GLM procedures (P˂0.05). The PR on d30 in control (43%) and resynch (48%) groups was non-significant. On d60 and d90 overall PR was 44 and 73% (P=0.002) and 43 and 72% (P=0.002) while overall pregnancy loss was 11 and 4% in control and resynch groups, respectively. In experiment II, PR on d30, d60 and d90 was 44 versus 54% (P=0.28), 53 versus 72% (P=0.03) and 50 versus 70% (P=0.025) in control and resynch groups with overall pregnancy loss of 14 and 3%. Mean P4 profile (ng/mL) was non-significant on d14 while significant on d16 and d30 post TAI in control and resynch groups. Mean luteal cross-sectional area on d30 post TAI has significant difference between both groups. In conclusion, a significant increase in overall PR in resynch group makes it an efficient reproductive management tool in comparison with control group.