A process for producing a sweetening composition which comprises mixing N-N-(3,3 -dimethylbutyl)- L-α-aspartyl- L-phenylalanine l-methyl ester and Aspartame, wherein the amount of the N-N-(3,3- dimethylbutyl)-L-α-aspartyl-L-phenylalanine l-methyl ester is between 0.1% by weight and 35% by weight based on the total amount of the N-N- (3,3-dimethylbutyl)-L-α-aspartyl-L-phenylalanine l-methyl ester and the Aspartame.