The effect of washing yeast cells on the ethanol productivity was examined on the repeated batch fermentation using beet molasses with the flocculent yeast strain M-9.Washing with acid chemicals such as sulfuric acid or phosphoric acid and chelate compounds such as disodium ethylenediaminetetraacetate (ED TA) effectively enhanced ethanol productivity, but the effect of washing did not continue for long periods. Furthermore, there was little bacterial contamination after repeated fermentation several times, and waste water after washing of yeast cells inhibited ethanol fermentation.These results suggested that the effect of washing was due to removal of inhibitory substances from the yeast cell surface rathar than the suppression of bacterial contamination.