Xanthan gum-water solutions with polymer concentrations 0.05-1% w/w and chromium ion content 30-1200 ppm were being gelled at temperatures from 25 to 90 degrees C. A control deformation test (CD test) at a constant shear rate 0.05 s(-1) was, performed for all the specimens. Shear moduli of elasticity and in some cases yield stresses and yield strains were determined from these tests. The energy of activation E-a = 93 +/-6 kJ/mol was obtained. The dependence of the gelation rate on the ionic concentration followed a power law with a coefficient of 1.8. There was relatively small dependence of the gelation rate on the xanthan gum concentration. Surprisingly, the maximum obtainable moduli at complete gelation do not depend on xanthan gum concentration in the range 0.2-1% w/w and are about 2400 Pa. The number of the bound chromium ions per monomer unit of xanthan gum is changed from 0.64 to 0.16 for the above measured concentrations of the polymer. High moduli gels on the base of the lower concentrations of xanthan gum were practically not recoverable after mechanical destruction. The assumption was made that the main reason for the profile modification of the flow for enhanced oil recovery in porous media is the yield stress of the gels. The smaller capillaries can even be closed if the yield stress is higher than the maximum shear stress existing in the capillary. (C) 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 160-166, 2007