This study was designed to compare commercially available extender Bioxcell with tris-citric egg yolk extender for post thaw quality and in vivo fertility of buffalo semen. For comparison of post thaw semen quality: semen was collected from five adult Nili-Ravi buffalo (Bubalus bubalis) bulls of similar age group with artificial vagina (at 42 degrees C) for three weeks (replicates). Qualifying ejaculates having motility >60% from each buffalo bull were divided in two aliquots and diluted (at 37 degrees C having 50 x 10(6) spermatozoa/ml) in tris-citric egg yolk or Bioxcell extender. Diluted semen was cooled to 4 degrees C in 2 hours, equilibrated for 4 hours and filled in 0.5 ml straws. Semen straws were kept over liquid nitrogen vapors (5 cm) for 10 minutes. Straws were then plunged and stored in liquid nitrogen (-196 degrees C). After 24 hours of storage, semen straws were thawed at 37 degrees C for 30 seconds to assess sperm motility, viability, plasma membrane integrity, normal apical ridge, and abnormalities (head, mid piece, and tail). For comparison of in vivo fertility: semen from two buffalo bulls of known fertility was cryopreserved in tris-citric egg yolk and Bioxcell as described earlier, and used for inseminations under field conditions. Post-thaw percentage of sperm motility (45.3 +/- 1.1, 45.0 +/- 1.4), viability (66.2 +/- 1.1, 64.4 +/- 1.3) plasma membrane integrity (60.4 +/- 1.2, 59.2 +/- 1.4) and normal apical ridge (82.9 +/- 0.5, 80.7 +/- 0.5) did not differ (P > 0.05) in tris-citric egg yolk and Bioxcell extender, respectively. Similarly, sperm abnormalities of head (1.20 +/- 0.1, 1.20 +/- 0.1), mid piece (0.67 +/- 0.1, 0.87 +/- 0.1) and tail (11.7 +/- 0.2, 11.6 +/- 0.3) remained similar (P > 0.05) in tris-citric egg yolk and Bioxcell extender, respectively. In vivo fertility rates of buffalo semen cryopreserved in tris-citric egg yolk and Bioxcell also remained similar (44% vs. 47%). It is concluded that commercially available Bioxcell may be used for the cryopreservation of buffalo semen with an equal efficiency to tris-citric egg yolk extender.