Pre-synchronization is an effective management strategy in lactating dairy cows to increase the number of animals in estrus and facilitate AI during a desired time interval. However, it is not a strategy often used in nulliparous dairy heifers. The objective was to characterize the distribution of detected estrus following a 14 d CIDR and prostaglandin F2α (PG) treatment as a pre-synchronization strategy in cyclic dairy heifers. Holstein heifers (n = 119) received a CIDR on d −30, and had the CIDR removed 14 d later on d −16. All heifers then received an Estrotect patch and were observed daily to facilitate detection of estrus. Following removal of the CIDR, 115/119 (96.7%) heifers were detected in estrus within 5 d. The proportion of heifers detected in estrus ± SE for each d after CIDR removal was: d 1: 12.6% ± 3% (15/119); d 2: 55.5% ± 5% (66/119); d 3: 18.5% ± 4% (22/119); d 4: 8.4% ± 3% (10/119); d 5: 1.7% ± 1% (2/119). Four heifers were not detected in estrus. Sixteen d after CIDR removal, all heifers received an injection of PG (25 mg i.m.) upon entry to the AI pen (study d 0). All heifers received tail paint and were observed for behavioral estrus daily. Following PG treatment, 114/119 (95.8%) heifers were detected in estrus within 5 d. The proportion of heifers detected in estrus ± SE for each d after PG treatment was: d 1: 3.3% ± 2% (4/119); d 2: 16.0% ± 3% (19/119); d 3: 59.7% ± 5% (71/119); d 4: 16.8% ± 3% (20/119); d 5: 0% (0). Five heifers were not detected in estrus. For the 2 estrus events observed, peak activity was detected 2 d after CIDR removal and 3 d after PG treatment. Pre-synchronization with a 14 d CIDR and PG protocol appears to be an effective strategy to facilitate detection of a high percentage of dairy heifers in estrus.