This work was undertaken for the evaluation and revision of group-additivity values necessary for predicting standard enthalpies of formation and enthalpies of vaporization of ethers, acetals, ketals, and ortho esters by means of Benson's group-additivity methodology. The database on the standard molar enthalpies of vaporization Delta(1)(g)Hdegrees(m) has been extended with measurements on several acetals, ketals, and ortho esters using the transpiration method. The standard molar enthalpies of formation Delta(f)Hdegrees(m) (g,298.15K) of alkyl ethers, acetals, ketals, and ortho esters were derived using the data for the Delta(f)Hdegrees(m) (1 or cr,298.15K) from the literature and the present results for the enthalpies of vaporization or sublimation. The current database of experimental data for enthalpies of formation and enthalpies of vaporization at 298.15 K have been used to reevaluate the values of the Benson's increments for of alkyl ethers, acetals, ketals, and ortho esters. The group-additivity parameters and strain corrections useful in the application of the Benson's correlation are presented in tabular form, together with a description of their evaluation.