The aim of the study was to evaluate the effects of exogenous fi brolytic enzymes on the in vitro ruminal fermentation of three tropical forages (Kikuyo grass 1 and 2 and Angleton grass).Three different enzyme preparations were tested: cellulase (CEL), xylanase (XYL) and a 1:1 mixture cellulase:xylanase (MIX).Dry matter disappearance was increased (P<0.05) by CEL and MIX for Kikuyo grass 1.The treatment of forages with CEL and MIX increased (P<0.05)NDF degradability, except for Kikuyo grass 2. CEL treatment also increased (P<0.05) total VFA production of Kikuyo grass 2 and Angleton grass.The results indicate that the treatment of tropical forages with cellulase stimulate their in vitro ruminal fermentation, but the xylanase enzyme used did not produce any positive effect.