Viscosities of aqueous solutions of La(NO3)(3), Ce(NO3)(3), and Pr(NO3)(3) in the concentration range of (0.2 to 1.0) mol(.)L(-1) were measured from (293 to 333) K. Relative viscosity data were interpreted in terms of the Jones-Dole equation, and values of ion-ion and ion-solvent interactions coefficients were evaluated. An empirical equation eta = a(0) exp(b(0)C + c(0)C(2)) was also applied to the viscosity data and values of coefficients a(0), b(0), and c(0) were calculated for all the three systems.