The dissociation constants of benzoic acid, p-methoxybenzoic acid and p-nitrobenzoic acid have been determined at $25^{circ}C$ in ethanol-water mixtures containing 0, 10, 20, 30, 40, 50, 65 and 80 weight % ethanol by the direct conductance measurements and the method involving titration of the acid sample with perchloric acid reagent. The results by the two methods have been discussed and compared with those by other methods.