The objective of the present study was to determine the efficiency of different protocols in inducing and synchronizing the estrus cycle of Saanen goats by using new or reused synchro-mate-B (SMB) and controlled internal drug release (CIDR) in combination with either equine chorionic gonadotrophin (eCG) or cloprostenol. Female goats (n=120) were divided at random into six groups of 20 animals each. In the T1-SMB group, the females were injected intramuscularly (i.m.) with 2.5mg estradiol valerate+1.5mg norgestomet and received a subcutaneous ear implant containing 2.0mg of norgestomet for 9 days. On the day of implant removal, the animals received 100IU of eCG and 0.05mg of cloprostenol. In the T2-SMB group, the animals were identically treated, except that the ear implant they received had been previously used in cattle. In the T3-SMB group, the treatment was identical to that for T1-SMB, but eCG was not administered. In the T1-CIDR group, the animals were treated for 9 days with an intravaginal device inpregnated with 0.3g of progesterone and injected i.m. with 100IU of eCG and 0.05mg of cloprostenol on the day of implant removal. The animals of the T2-CIDR group were treated like those of the T1-CIDR group, except that the intravaginal implant they received had been previously used in goats. The animals of the T3-CIDR group were treated like those of the T1-CIDR group, but did not receive eCG. The percentages of estrus and fertility were 100/80% (T1-SMB), 90/80% (T2-SMB), 75/75% (T3-SMB), 100/95% (T1-CIDR), 100/100% (T2-CIDR) and 70/65% (T3-CIDR), respectively, with the results for both parameters being lower (P