Provided is a method for the production of aminodicarboxylic acid N,N-diacetic acids of formula (I), wherein X is independently hydrogen or an alkali metal and n is 1 or 2. Aminodicarboxylic acid-N,N-diacetic acids of high purity can be yielded. The method involves: a) reacting an aminodicarboxylic acid, with 0.8 to 1.2 mole equivalents of formaldehyde and with 0.8 to 1.2 mole equivalents of hydrocyanic acid; b) reacting the reaction products of a) with 0.8 to 1.2 mole equivalents of hydrocyanic acid and with 0.8 to 1.2 mole equivalents of formaldehyde; c) hydrolyzing in the reaction product obtained in b).