An attempt has been made to find out if the organic matter digestibility of tropical feeds and fodders can be predicted from the results of anin vitrocellulase enzyme technique. Thein vivodigestibility coefficient of 27 tropical feeds and fodders was determined in wethers. The enzyme insoluble organic matter content of these feeds was determined using a cellulase enzyme technique. The indigestible OM (g/kg feed DM)in vivo(y) was plotted against enzyme insoluble organic matter (g/kg DM) (x). The equation is y = 60+0.817x, R2= 0.95; RSD = 32 g/kg DM. Equations for predicting DOM (g/kg DM) and digestibility of OM (%) are calculated. The testing of the equation on an independent data base of 40 individual feeds and fodders showed that the validity of the equation is fairly general.