In vivo experiments are the preferred method for ruminant feed evaluation, but they are very expensive, laborious and time-consuming. In situ and in vitro techniques are commonly used as a routine all over the world as a predictor of in vivo results. In situ assays have been the basis of many feed evaluation systems due to its ease of use and low cost. In vitro techniques, such as gas production, give an opportunity to get similar information plus a better description of fermentative kinetics. The aim of this work was to compare data obtained from in vivo, in vitro and in situ assays for the evaluation of three tropical forages used in ruminant nutrition in Brazil.