A new model for calculating the viscosity of aqueous solutions has been developed. Parameters for 74 solutes were established based on a critical review of the literature for solutions of one solute in water, with over 9000 points included. The average difference between the calculated and experimental viscosities is less than 0.1 %, and the standard deviation of this difference is 3.7 % of the average experimental viscosity. The model was validated by estimating published viscosity for systems of more than one solute in water. The average difference between experimental and calculated values for 1700 points is -2.7 %, and the standard deviation of this difference is 16 % of the average experimental viscosity. The median standard deviation of the difference between experimental and calculated values is 3.5 % of the experimental viscosity. The solutes studied are (NH4)(2)SO4, AlCl3, BaCl2, Ca(NO3)(2), CaCl2, Cd(NO3)(2), CdCl2, CdSO4, CoCl2, CoSO4, Cr-2(SO4)(3), CrCl3, Cu(NO3)(2), CuCl2, CuSO4, Fe-2(SO4)(3), FeCl2, FeSO4, H2O2, H2SO4, H3PO4, HCH3CO2 (acetic acid), HCHO2 (formic acid), HCl, HCN, HNO3, K2CO3, K2Cr2O7, K2HPO4, K2SO4, K3PO4, KBr, KCH3CO2, KCHO2, KCl, KH2PO4, KI, KNO3, KOH, Li2SO4, LiCl, LiNO3, LiOH, Mg(NO3)(2), MgCl2, MgSO4, MnCl2, MnSO4, Na2CO3, Na2HPO4, Na2S2O3, Na2SO3, Na2SO4, Na3PO4, NaBr, NaCH3CO2, NaCl, NaClO3, NaF, NaH2PO4, NaI, NaNO3, NaOH, NH3, NH4Cl, NH4NO3, NiCl2, NiSO4, Pb(NO3)(2), Sr(NO3)(2), SrCl2, sucrose, ZnCl2, and ZnSO4. Density data are also presented for these solutes and for NaHCO3.