This research has been undertaken to show the application of specific ion interaction theory (SIT) for the complexation of dioxovanadium(V) with nitrilotriacetic acid (NTA) at different ionic strengths of (0.1 to 1.0) mol center dot dm(-3) sodium perchlorate as supporting electrolyte and pH range of 1.00 to 2.50 at 25 C. Two species, VO(2)HL(-) and VO(2H)L, have been detected according to curve fitting, which enables us to calculate the values of stability constants. Ionic strength dependence semiempirical parameters for the dissociation and stability constants were derived on the basis of an extended Debye-Huckel-type equation. The SIT model successfully described the ionic strength dependencies of the stability constant values.