The objective of the study was to compare Menke et al.’s buffer (1979) with Zhao and Lebzien’s buffer (2000) on gas production, pH and NH₃-N of 16 feedstuffs for ruminants in in vitro incubation. The gas production was recorded after incubation at 12 and 24 h. The pH and NH₃-N concentration of incubation residues were determined after incubation for 24 h. The results showed that there was no significant difference in in vitro gas production, pH and NH₃-N concentration between the two buffers (P>0.05). It was found that in vitro gas production, pH or NH₃-N concentration of the two buffers were significantly correlated (P<0.05). It was concluded that the two buffers had similar results on in vitro gas production, pH and NH₃-N concentration in in vitro incubation. It is suggested to compare these two buffers on volatile fatty acids (VFA) concentration and rumen microorganism activities in the future.