Cryopreservation of oocytes is an open problem as a result of their structural sensitivity to the freezing process. Buffalo oocytes are sensitive to chilling injury, making their cryopreservation very difficult. To improve the efficacy of vitrification in buffalo oocytes, two experiments were conducted in this study, the first one was to evaluate the effect of existence of cumulus cells on the viability and maturation of vitrified oocytes. Oocytes with complete
cumulus oocyte complexes (COCs), partial (COCs) and denuded
were matured in vitro for 22h. The oocytes were vitrified in a mixture of 3M DMSO + 3M EG by the straw method. After warming the oocytes were cultured for further 2h. There was significant increase in morphologically normal, survivability and maturation rate of COCs and partial COCs than denuded oocytes. The second experiment was to evaluate the effect of meiotic stage on
the viability and maturation of vitrified oocytes. Mature (22h) and immature (0h) oocytes were vitrified by the straw method. After
warming, the oocytes were evaluated morphologically, and then cultured in vitro to complete the maturation period to 24h. Survivability of vitrified oocytes directly after warming was higher significantly (P< 0.05) in mature than immature oocytes. Also, the nuclear maturation rate was significantly higher (p