[en] Dielectrometry, conductometry, IR-spectroscopy are used to study dimethyl sulfoxide complexing with iodine in binary system and in CCl₄, C₆H₆, C₆H₅Cl, C₆H₅CF₃, 1, 2-dichloroethane solutions. Complexes of 1:1 composition are formed in solutions, in the binary system of 2:1 and 2:2 composition. I₂ molecules add to oxygen atoms. In CCl₄ and in binary system gradual transformation of so called external charge transfer complexes (CTC-1) to internal ones (CTC-2) that are described by the 1st order reaction kinetic equations is observed. On dissolution of CTC of 2:2 composition they disproportionate into two CTC molecules 1:1. Enthalpy of forming CTC-1 1:1 is approximately 4 kcal/mol, CTC-2 1:1 - 8, CTC-1 2:1 - 8 kcal/mol