An attempt is made to correlate the Viscosity of crude fractions with other characteristics. The following equation is derived by stepwise multiple regression: log nu = 1.37(d log M)(2) + 16.12(d log M)(-2) -9.06 where nu is the kinematic viscosity (mm(2)s(-1)) of the crude fraction at 50 degrees C, d the specific gravity and M the molecular weight. The calculated viscosity has an average absolute deviation of 15.9%. Comparison between the average deviation calculated from the equation and that from local correlations for connate crude fractions shows that this equation is applicable not only to a variety of crude fractions but also to those belonging to a specific group.