To maintain a calving interval of 13-14 month in buffaloes, successful breeding must take place within 85-115 days (d) after calving. Complete uterine involution and resumption of ovarian activity and heat expression usually takes place around 20-50 d post partum (dpp); therefore, there is a window of 35-95 d to rebreed a cow and get her pregnant to maintain the desired calving interval. Although artificial insemination (AI) has the potential to make a significant contribution to genetic improvement in buffaloes, its practical application has been difficult because poor estrus expression by cows and poor estrus detection by humans, a variable duration of estrus and the difficulty to predict time of ovulation. More recently, the development of protocols for synchronization of ovulation and fixed timed insemination (TAI) in buffaloes have been used to overcome these constrains and be able to use more extensively AI in commercial herds. Nevertheless, resynchronization of ovulation and TAI still remains a problem herds managed under extensive conditions for similar reasons abovementioned. Very recently, we did four field trials to study the efficacy of different protocols that combined use of GnRH, or estradiol benzoate (EB), prostaglandin (PGF) and intravaginal progesterone (P4) releasing device (PIVD) or norgestomet ear implant (NOR) to resynchronize estrus and ovulation at day 18 post AI in buffalo cows under commercial conditions.