The study was carried out to detennlne if the addition of cysteamine to the culture medium buffalo oocytes would improve its intracytoplasmic glutathione (GSH) levels and if such changes would translate an improvement in the male pronucleus (MPN) and developmental capacity. In Experiment 1, buffalo oocytes were cultured in basic maturation medium composed of TCM 199 + FCS (10%v/v) + gonadotropins with or without cysteamine. The addition of 50 mM and 100 mM cysteamine resulted in 75% and 81% MPN formation, respectively, of the in vitro fertilized oocytes. ln Experiment 2, the proportion of cleavage stage embryos was greater for oocytes that were matured In the presence of cysteamine (46/96) compared to the control (27/90). The percentage of cleaved embryos developing up to the blastocyst stage was 19.3% with cysteamine and 11.1% without cysteamine supplementation. In Experiment 3, intracytoplasmic glutathione levels were measured for oocytes matured in the presence or absence of cysteamine. Intracytoplasmic GSH values improved when oocytes were matured in maturation conditions supplemental with cystamine. However, the values were lowered compared to the GSH levels of large follicles representing the In vivo matured oocytes. The results of the present study suggest that an increase in the intracellular GSH of bubaline oocytes induced by cysteamine during maturation may provide favorable intracellular condition to support fertilization and embryonic development of oocytes in vitro.