The objective of this study was to evaluate the efficacy of cloprostenol (CLO) or aglepristone (ALI) for pregnancy termination in queens at 21–22 and 35–38 days of gestation. Two experiments (EXP) were carried out to accomplish this aim. Thirty-seven 12- to 14-month-old mixed breed queens were used in a randomized design. At oestrus, queens were housed for mating with a tom, and pregnancy was confirmed by transabdominal ultrasonographic examination (US). On days 21–22 of pregnancy (EXP1) or 35–38 of pregnancy (EXP2), queens were divided into three groups (G). Queens in G1 received ALI (10 mg/kg, sc; EXP1, n = 6; EXP2, n = 6) on two consecutive days. Queens in G2 received CLO (5 μg/kg, sc; EXP1, n = 6; EXP2 = 7) on three consecutive days. Queens in G3 received 1 ml of saline solution (PLA, sc; EXP1, n = 6; EXP2 = 6). After treatment, females were monitored daily by US during for 10 days and weekly until the end of gestation. In EXP1, pregnancy was terminated in (6/6, 100%), (0/6, 0%) and (0/6, 0%), for the ALI, CLO and PLA groups, respectively (p < 0.001). In EXP2, pregnancy was terminated in (6/6, 100%), (1/7, 14%) and (0/6, 0%) for the ALI, CLO and PLA groups, respectively (p < 0.001). In both EXP, after CLO administration, animals vomited and were depressed for 30 min; but no side effects were observed in the animals in the ALI group. In conclusion, the results from this study indicate that three injections of CLO are not effective, but two injections of ALI are effective to induce abortion in queens at 21–22 or 35–38 days of pregnancy.