Boiling points (T-B) of acydic alkenes are predicted from their boiling point numbers (Y-BP) with the relationship T-B(K) = -16.802Y(BP)(2/3) + 337.377Y(BP)(1/3) - 437.883. In turn, Y-BP values are calculated from structure using the relationship Y-BP = O-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 O-i is a parameter that depends on the substitution pattern of the alkene, while the rest of the equation is the same as that reported earlier for calculating the Y-BP values of alkanes. For a data set consisting of 250 acyclic alkenes having from 6 to 36 carbon atoms, the average absolute deviation between literature T-B values and those predicted with these equations was 1.29 K, and the R-2 of the correlation was 0.999. In addition, the calculation of boiling points by this method provides a useful means to predict the flash points of alkenes from structure.