A generalized correlation in terms of the reduced molar refraction (parameter r) is proposed for the calculation of the viscosity of dense hydrocarbon fluids. The input parameters are the refractive index and density at 20 degreesC, molecular weight, critical temperature, and pressure. For more than 2600 data points used for the evaluation of the proposed correlations, the average deviation for liquids for hydrocarbons from C-1 to C-20 is about 8%. For saturated gases (P-r < 1), the absolute average deviation is 3.5%, whereas for high-pressure gases (1 < P-r < 10) and for hydrocarbons from C-1 to C-10 the average deviation is about 11%. A comparison with similar generalized correlations shows that molar refraction is a suitable third parameter for the generalized correlation of transport properties of dense hydrocarbons.