The influence of salt concentration on the size and on the thermodynamic stability of interpolymer complexes composed of oppositely charged macroions having different affinity to solvent was studied from a theoretical viewpoint. It was shown that increasing salt concentration causes changes in the structure of complex particles. At low salt concentration, the particles preserve their structure and size. At a critical salt concentration, n(S)(cr), the particle size rises sharply to a slightly larger dimension. From this concentration, the macroions forming the interpolymer complex start to separate, and the complex is fully destroyed at a salt concentration n(S)*. After separation, the macroions coexist in solution and with further increase in salt concentration reduce their sizes according to the screening of polyion charges by salt ions. n(S)(cr) and n(S)* depend on physical parameters such as the degree of polymerization of macroions, their degree of ionization, and macroion-solvent interaction parameters. Experimental data collected in the particular cases of PLL-PLCA and PLL-PLCAI complexes with polylysine qualitatively agree with the trends indicated by the theoretical approach.