Viscosities of uranium solutions in H2O and 3 mol/L HNO3 medium were measured by Ubbelhode flow vis-cometer in the concentration range of 0.5%u001f3.0% from 10 篊 to 30 篊 at 5 篊 interval. Viscosity data were interpreted in terms of an empirical equation; h =aoexp(boM+coM2). Values of coefficients ao, bo and co were calculated for all the three systems studied. Flow activation energies and thermodynamic parameters were also evaluated. Viscosities of uranium solutions in H2O and 3 mol / L HNO3 medium were measured by Ubbelhode flow vis-cometer in the concentration range of 0.5% u001f3.0% from 10 篊 to 30 篊 at 5 篊 interval. Viscosity data were interpreted in terms of an empirical equation; h = aoexp (boM + coM2). Values ​​of coefficients ao, bo and co were calculated for all the three systems studied. Flow activation energies and thermodynamic parameters were also evaluated.