The effect of a commercial inoculant on the fermentation quality of silage made from agricultural byproducts (ABP silage) prepared in Thailand was examined. By adding an inoculant, the pH of silage became low and the counts of yeast and clostridia in silage decreased in comparison with the silage without inoculant. The effect of temperature against the inoculant was also examined by using a modified pouch method. The addition of inoculant provided good quality silage at 30°C. However at 45°C, the addition of the inoculant resulted in a remarkable decrease in the amount of lactic acid produced and an increase in pH about 0.6-0.8 with no good quality silage produced. From these results, it was suggested that the inoculant used in this study was effective for improving the fermentation quality of ABP silage in Thailand at temperatures less than 37°C, but was not effective at 45°C.