The composition of the ruminal flora and the VFA concentration were surveyed in the water buffalo found in tropical Asia. The results showed that the average concentration of VFA in rumen contents was 57 mM and the number of bacteria and protozoa was 1010 and 106 per ml, respectively. Acetic acid comprised the major portion of the individual VFA followed by propionic acid. Among the rumen bacteria Gram-negative rods were most predominant followed by Gram-positive cocci. Four new species of rumen protozoa have been found in the water buffalo in tropical Asia i.e. Entodinium ogimotoi, E. bubalum, E. fujitai and E. tsunodai. The rumen ciliate composition was compared among water buffalo found in different regions of the world.