Boiling point numbers (Y-BP) of allcylbenzenes are predicted directly from the molecular structure with the relationship Y-BP = Ar-i + 1.726 + 2.779C + 1.716M(3) + 1.564M + 4.204E(3) + 3.905E - 0.329D + 0.241G + 0.479V + 0.967T + 0.574S. Here, Ari is a parameter that depends upon the substitution pattern of the aromatic ring, while the remainder of the equation is the same as that reported earlier for calculating the Y-BP values of alkanes. The boiling points (T-B) of the alkylbenzenes are then calculated from the relationship T-B (K) = -16.802Y(BP)(2/3) + 337.377Y(BP)(1/3) - 437.883. For a data set consisting of 130 allcylbenzenes having 7-40 carbon atoms, the average absolute deviation between the literature and predicted T-B values was 1.67 K and the R-2 of the correlation was 0.999. In addition, Y-BP values calculated with this method can be used to predict the flash points of the alkylbenzenes.