To determine estrous, ovarian and reproductive responses after different prostaglandin(PG)-based protocols, ewes were assigned to groups PG10, PG12, PG14 or PG16 (two PGinjections administered 10, 12, 14 or 16 days apart; respectively). Experiment I (n = 132) wasconducted to evaluate the estrous response, ovulation rate (OR), conception and fertility.Experiment II (n = 24) was conducted to evaluate ovarian follicle growth, steroid concen-trations and the interval from the second PG injection to estrus (PG-estrus) and ovulation(PG-ovulation). Estrous response was less with the PG16 (P 0.05). From 8 to 4 days before estrus, progesterone (P4) concentrationswere greater for the PG14 and PG16 than for the PG10 and PG12 (P