The flash point of hydrocarbons and petroleum mixtures is important safety-related data for processing and handling of these materials. In this paper, experimentally measured data on flash points of about 140 pure hydrocarbons and petroleum fractions were collected and used to evaluate existing methods for prediction of these data available in the literature. The errors for the available methods varied from 1.6 to 4.9% for pure hydrocarbons and from 3.7 to 11.1% for petroleum fractions. In these methods, parameters such as vapor pressure, boiling point, molecular weight, density, activity coefficient, and composition were used. On the basis of the available methods and simplified relations for vapor pressure prediction, it was found that the ratio of the flash point to the boiling point of hydrocarbon systems and their mixtures is a constant and a value of this constant is about 0.7 when both temperatures are expressed in absolute degrees. The average absolute deviation for this simplified method was 1.7% for pure hydrocarbons and 2.8% for petroleum fractions, which is comparable or better than existing methods.