The inhibition of the plasma membrane-bound ATPase of S. cerevisiae KCTC1205 was studied for two hydrophobic inhibitors, diethylstilbestrol (DES) and N,N`-dicyclohexylcarbodiimide (DCCD). DES showed nearly noncompetitive inhibition kinetics (K_(EI)/K_(ESI)= 0.43-1.57), which suggested non-overlapping binding sites for MgATP and DES. For the present, however, indirect and nonspecific action of DES through membrane lipid can not be excluded. For DCCD inhibition, near first-order reaction kinetics (n = 0.79 with respect to DCCD) was observed. This suggested an inhibition resulting from the reaction of a single molecule of DCCD with a single site on ATPase. For the covalent inactivation reaction, a second-order rate constant of 7.4±1.3 sec^(-1)M^(-1) was calculated. For DES there were only minor effects of pH on the inhibition, while higher reactivities were observed for DCCD at acidic pH`s in the range of 4 to 7.