Using group additivity values to estimate Delta(vap)H degrees(298) and the Kistiakowsky equation to estimate both Delta(vap)S degrees(T-b) and Delta(vap)H degrees(T-b) at the boiling point (T-b), it is shown how an average value of Delta(vap)C(p)degrees can be obtained which can then be used to calculate values of Delta(vap)S degrees(298). This latter can then be used in conjunction with S degrees(g,298) to calculate S degrees(l,298). Alternatively, where values of S degrees(l,298) are available but not SO(g,298) the latter can be calculated. The method applies to regular liquids, even those with relatively large dipoles but not to H-bonded liquids. The accuracy of estimated values of S degrees(l,298) are 0.45 +/- 0.16 cal/(mol K) with a maximum deviation of 1.0 cal/(mol K) for an assortment of 14 selected compounds and 0.3 +/- 0.12 for another 17 liquids for which groups are not available but Delta(vap)H degrees(298) and Delta(vap)S degrees(298) are. Here the largest deviation is 1.9 cal/(mol K). Calculated values of C(p)degrees(l,298) are much less accurate, +/-3 cal/(mol K) with a maximum deviation of 9.0 cal/(mol K). It is also shown that the best average value of C(p)degrees to use in calculating changes in Delta H degrees and Delta S degrees in a specified temperature interval, T-1 to T-2, is the arithmetic mean of the initial and final values, [C(p)degrees(T-1) + C(p)degrees(T-2)]/2. Changes are recommended in some of the group values for calculating Delta(vap)H degrees(298) and also in the group O-(C)(2) for calculating gas-phase entropies of ethers and for N-(C)(2)(H) for calculating entropies of secondary amines.