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This study was designed to determine the effect of thioglycol in extender on fertility of cryopreserved buffalo semen under filed conditions. For this purpose, semen from two Nili-Ravi buffalo (Bubalus bubalis) bulls of known fertility was split-sampled and diluted with tris-citric acid extender either containing thioglycol or without thioglycol (control) at 37°C having approximately 50 × 106 spermatozoa ml-1. Diluted semen was cooled to 4°C in 2 h at the rate of 0.275°C minute-1 and equilibrated for 4 h at 4°C. Cooled semen was then split into two aliquots, filled in 0.25 and 0.5 ml straws at 4°C, kept on liquid nitrogen vapours for 10 minutes and plunged in liquid nitrogen for storage. The cryopreserved semen was used to perform artificial insemination in buffaloes and fertility rate based on 90-days first service pregnancy was determined under field conditions. The overall fertility rate was found higher in extender containing thioglycol compared to control 56 vs. 44%, respectively. It is concluded that thioglycol in tris-citric acid extender improves the fertility of cryopreserved buffalo semen under field conditions.