Infertility caused by smooth inactive ovaries (SIO) is a common ovarian disorder that causes a major reproductive failure in dairy cows and has a significant economic impact on the dairy industry. The present study aimed to investigate the response of dairy cows with a syndrome of smooth inactive ovaries to different hormonal treatment protocols and their impact on reproductive performances. Lactating multiparous Holstein cows (n= 75) having smooth inactive ovaries diagnosed by two successive ultrasonographic examinations performed at 10 days interval were used in this study. Cows were assigned randomly into 5 groups (15 each). Group A, treated with a single injection of 250 µg GnRH, Group B with a single injection of 2500 IU HCG, Group C, in which cows received CIDR for 7 days and PGF2α at day 6 (24 hours before removal of CIDR followed by injection of 250 µg GnRH (at day 8) 24 hours after removal of CIDR (at day 8)(CIDR, PGF2α and GnRH), Group D in which cows received CIDR for 7 days and PGF2α at day 6 (24 hours before removal of CIDR) followed by injection of 2500 IU hCG 24 hours after removal of CIDR (CIDR, PGf2α, and HCG), and Group E in which cows did not receive any treatment and kept as a control group. The results showed that CIDR+ GnRH and CIDR+ hCG protocols achieved the full (100%) estrus induction rate (EIR). hCG group achieved 93% and GnRH group 80%, while the control group only achieved 20% EIR. The shortest treatment estrus intervals (TEIs) were recorded in CIDR+ hCG and CIDR+ GnRH protocols. Mean±SD of TEIs were 1 ± 0, 1.4 ± 1.1days 10.4 ± 5.4, 16.7 ±7.1 and 23.7± 2.9 days in CIDR+ hCG . CIDR+ GnRH, HCG, GnRH and control groups respectively.  The CIDR+ hCG group had the highest pregnancy rate (86.7%), followed by hCG (79.9%) and CIDR+ GnRH groups (80%), and GnRH group with 73%. The control group showed a 13.3 % pregnancy rate however, GnRH group showed the highest total conception rate (91.6%). It was concluded that the highest EIR and shortest TEI were obtained in CIDR+ GnRH and CIDR+ hCG protocols. While the CIDR+ hCG group had the highest pregnancy rate (86.7%).