The thermal balance of a constant speed stationary compression ignition engine operating on diesel, ethanol-diesel blends and fumigated ethanol was established at different loading conditions of the engine, The thermal balance was in respect of useful work, heat lost to cooling water, heat lost through exhaust, heat carried away by the lubricating oil and other losses (unaccounted-for losses). The results indicate that the thermal balance of the engine operating on 5 and 10% ethanol-diesel blends and fumigated ethanol was not significantly different at the 5% level of significance when compared to diesel. However, in the case of 15 and 20% ethanol-diesel blends, the thermal balance was significantly different compared to diesel.