The step dissociation constants of ethylenediamine-N,N′-diacetic-N,N′-dipropionic and ethylenediamine-N,N,N′,N′-tetrapropionic acids at 298.15 K and ionic strengths of 0.1, 0.5, and 1.0 (KNO3) were determined potentiometrically. The results were extrapolated to zero ionic strength by the equation with one individual parameter. The thermodynamic constants of dissociation were calculated. The results are compared with the corresponding data on related compounds.