The saponification rates (measured at 25 ° by a titrimetric method) of the unprotonated forms of the methyl esters of glycine, alanine, leucine, valine, and phenylalanine were compared with those of theN-methyl, theN-acetyl, and theN-acetyl,N-methylamino acid analogues.N-Acetylation slightly increased or decreased the rate butN-methylation caused a reduction by as much as a factor of ten, depending on the complexity of the side-chain. The esters of theN-acetyl,N-methylamino acids, which exist ascisandtransisomers, were saponified at rates intermediate between those of the esters of theN-acetylamino acids andN-methylamino acids. Activation parameters were obtained for the phenylalanine and leucine derivatives.N-Methylation resulted in an increase in ΔH≠and ΔS≠which was attributed in part to solvation effects. The hydrolysis of the cationic esters of glycine and alanine was still evident at pH11.0.N-Methylation had little effect on the rates of saponification of the charged forms.