Initial rate studies of the forward reaction, for Yeast Alcohol Dehydrogenase, were carried out with varying concentration of several straight chain aliphatic monoamines and diamines over the pH range from 8.0 to 10.5. Aliphatic amines appear to either activate or inhibit Yeast Alcohol Dehydrogenase for a pH less than or greater than 9.5 respectively. The concentration of the amine enhances the observed activation or inhibition. The rotonated amine activates while the nonprotonated amine inhibits the enzyme. When both amine species are present in solution the observed effect will depend on the magnitude of the two opposing reactions. The rotonated amine acts as a modifier for the enzyme while the nonprotonated amine competes with B-nicotinamide adenine dinucleotide for the coenzyme active site. All data were treated by a weighted least squares method.