The objective of this study was to compare the efficiency of cloprostenol and fenprostalene in synchronizing estrus. Before treatment, estrus was detected during 4.5 d for multiparous cows in exp. 1 (n = 105) and 7.5 d for primiparous and nulliparous females in exp. 2 (n = 86). Females that were not in estrus (exp. 1: n = 74 and exp. 2: n = 58) received at random, either 500 μg of cloprostenol (i.m.) or 1 mg of fenprostalene (s.c). Cattle synchronized with cloprostenol or fenprostalene that presented estrus within 5 d showed similar fertility rates (exp. 1: 86.1% vs. 88.0% and exp. 2: 89.3% vs. 72.2% for cloprostenol and fenprostalene, respectively) and PGF2α-estrus intervals (exp. 1: 68 h vs. 73 h and exp. 2: 57 h vs. 57 h). However, the incidence of synchronization (exp. 1: 97.3% vs. 67.6%, P < 0.001; and exp. 2: 93.3% vs. 64.3%, P < 0.01) and pregnancy rates (exp. 1: 83.8% vs. 59.5%, P < 0.05; and exp. 2: 83.3% vs. 46.4%, P < 0.01) were statistically higher for cloprostenol than for fenprostalene. In exp. 2, primiparous cows and heifers obtained similar reproductive performances. The fertility rate of cattle treated with cloprostenol in exp. 2 was higher than that of untreated cattle (89.3% vs. 50.0%, P < 0.001, n = 56). In exp. 1, the variance of interval to estrus was similar for both analogues, but in exp. 2, it was less variable after the administration of cloprostenol (P < 0.05). Intervals between cloprostenol injection and estrus (0–10 and 0–15 d) were shorter (P < 0.05) and less variable (P < 0.001) than fenprostalene–estrus intervals. These results indicate that cloprostenol has a better potential for estrus synchronization than fenprostalene. Key words: Cloprostenol, fenprostalene, estrus synchronization, prostaglandin F2α, beef cattle