A group-contribution method has been developed for predicting the vapor pressures of organic liquids. The parameters for 42 organic groups are derived from 5359 experimental vapor pressure data on 342 organic compounds. The various group values are presented as four-constant expressions and can be used to estimate the vapor pressures of organic liquids up to 8000 kPa. With the proposed method, vapor pressures have been calculated for 336 organic compounds, and when compared with the experimental data, this method produces an average absolute percentage deviation of 5.0%. The proposed method is quite general and relatively easy to use. The required input parameters are the group numbers and the molecular weight of that compound.