Abstract: Polymers used in enhanced oil recovery operations, including polysaccharides, polyamides and cellulose derivatives may be crosslinked by the use of organic nitrogen compounds bearing at least two positively charged nitrogen atoms. Suitable crosslinking agents include the salts of aliphatic and aromatic diamines and bis (quaternary ammonium) compounds. The crosslinked copolymers may be used for mobility and permeability control purposes. The crosslinking agents are effective over a wide range of pH conditions to form stable gel structures with the polymers.