The aim of the study was to evaluate the effects of exogenous fibrolytic 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.