In order to elucidate the mechanism of induction of serum immunoglobulins polyreactive properties by chaotropic ions, gel-chromatography of immunoglobulins in the medium containing 3.3 M KSCN, has been done. It was found that the transformation of serum immunoglobulins to polyreactive antibodies, which could react with different serological unrelated antigens, was not followed by dissociation of any hypothetical blocking factors. Instead, it was demonstrated that the appearance of polyreactive properties of immunoglobulins was likely to depend on conformational changes of immunoglobulin molecules.