Formation of interpolymer complexes of poly( 5-vinyltetrazole) and poly(5-izopropenyltetrazole) with poly(acrylamide), poly(ethy1ene oxide), poly( 1-vinylpyrrolidone), and poly( 1vinyl-1,2,4-triazole) was investigated by potentiometry and viscometry. The reduced activity of tetrazol-containing polyacids in reaction with poly( 1-vinylpyrrolidone) from polyacrylic polyacids was explained by steric hindrances at the expense of bulky tetrazolic rings. There is a strong system of hydrogen bonds in the poly(5-vinyltetrazole) solution that leads to decreasing of its activity in the complexation in comparison with poly(5-izopropenyltetrazole). Hydrophobic interactions between methyl groups of poly(5-izopropenyltetrazole) lead to additional stabilization of the complexes at low degrees of ionization and to fast destruction of them at ionization degrees corresponding to destruction of the compact conformation of poly(5-izopropenyltetrazole) (a = 0.2-0.4). Interaction of poly(5-vinyltetrazole) with poly(l-vinyl-1,2,4-triazole) at elevated pH leads to an interpolymer complex stabilized by donor-acceptor interactions between the *-systems of tetrazolate anions and triazole rings.