A good hay-inoculum appears as appropriate as, more practical and giving more reputable results than, a hay plus concentrate or a maize silage-inoculum, in predicting the apparent digestibility of whole plant maize from the in vitro gas-test technique. The curve adjustment with 6 fermentation times (omitting the 96 h recording time) is as good as that with 7 fermentation times. The gas production after 24 h incubation is a better predictor than a plus b of the mathematical adjustment. Less accurate than cellulase, it almost comes up with it when taken in combination with CP content. However, both the gas-test and the cellulase techniques are less efficient than the NIRS technique in predicting maize digestibility.