It was shown that the monomeric rhodium sulfate complexes [Rh(H2O)(4)(SO4)](+), trans-[Rh(H2O)(2)(SO4)(2)](-), cis-[Rh(H2O)(2)(SO4)(2)](-), and [Rh(SO4)(3)](3-) were not predominant forms in aqueous solutions. The Rh-103 NMR chemical shifts of the complexes were assigned, and the conditions for their formation in solutions, concentration parameters, and acidity at which the fraction of the monomers was maximal were determined. The constants of formation of the complexes and ion pair (IP) were estimated: K (IP) = 8 +/- 3.5, K (1) a parts per thousand 8, K (2trans) a parts per thousand 1, K (2cis) a parts per thousand 1, and K (3) a parts per thousand 2.