PhYsical properties of neat tallow methyl ester and ethanol blends were determined to find the ester/ethanol blend which had the same viscosity as that of number 2 diesel fuel. Tallow ester and ethanol in a 65:35 (v/v) ratio gave the same viscosity as that of diesel fuel. This blend was mixed with number 2 diesel fuel in ratios varYing from 0 to 100%, and viscosities, densities and cetane indexes of the blends were determined Mixture viscosity was not affected by ester content. Viscosity of the mixture decreased as temperature increased. The cetane number of the tallow ester/ethanol/diesel blend was greater than that of pure number 2 diesel fuel. The cetane number of 56 for the tallow ester/ethanol blend was reduced to 46 for a blend of 25% tallow ester/ethanol and 75% diesel fuel. It was concluded that tallow ester had potential as a diesel fuel substitute.