A group-contribution model for the prediction of vapor pressures of organic solids is presented, based on the concept of the hypothetical liquid. The group-contribution parameters are applied in the prediction of vapor pressures for a variety of organic solids involving aliphatic and aromatic hydrocarbons, halogenated hydrocarbons, oxygenated hydrocarbons (alkanols, phenols, acids and ketones), and some multifunctional ones. Satisfactory results are obtained with errors below one order of magnitude down to very low pressures well below the Pa level. The required entropy of fusion is also predicted with a simple group-contribution method developed. The obtained predictions are-as expected from a simple method-not very accurate, but sufficient for the purpose of this study. Extrapolation, finally, of the method in the liquid range up to 1 atm. gives satisfactory predictions provided that the temperature range of the vapor pressure data is not far beyond that involved in the parameter estimation. (C) 2003 Elsevier Science B.V. All rights reserved.