Equilibria established in reactions between isophthalaldehyde (IPA) and terephthalaldehyde (TPA) on one side and 2-aminoethanol and NH3 on the other side were followed in solutions, where these amines acted both as reagents and as buffers. The equilibrium between TPA and 2-aminoethanol was followed spectrophotometrically; all others, of reactions of TPA with NH3 and of IPA with both NH3 and H2N-CH2-CH2-OH, were followed by using polarography. Separate limiting reduction currents of the dialdehyde and its imine enable simultaneous determination of the starting material and the product. The equilibria are shifted more in favor of the imine in reactions of TPA than those of IPA. Equilibrium constants for reactions of both TPA and IPA with 2-ammoethanol are 3 orders of magnitude higher than those observed for the reactions of dialdehydes with NH3, even when the pK(a) values of these two reagents differ only slightly.