Effect of concentration of salts and of the charge of metal ion on swelling behavior, composition and structure of the gels of poly(2-acrylamide-2-methyl-1-propanesulfonic acid) (PAMPS) salts in aqueous medium was studied. In the solutions of sodium and calcium chlorides the gel is swollen whereas in the presence of cobalthexammine(III) or iron(III) chlorides it collapses. In the collapsed gels the ratio Q between the number of charges of the network and that of trivalent metal ions in the gel phase is close to stoichiometric. At high concentrations of multivalent salts the marked increase of Q is observed and the gets swell. The collapse and the reentrant swelling of the gel in the solutions of iron salt occur in the same ranges of concentrations where precipitation and redissolution of linear polymer is observed. The collapse of PAMPS gel in the presence of trivalent metal ions is explained by the formation of salt bridges between polymer ions and the cations of metal via the electrostatic forces. At high excess of metal ions into the gel these bridges are destroyed due to competition interactions with the ions of inorganic salt.