The reference interaction site model (RISM) has been applied to elucidate the effect of pressure on the partial molar volumes V-2(0) at infinite dilution. The system under consideration consists of monoatomic solvent and mono-, di-, tri-, and tetraatomic solutes and is subject to the Lennard-Jones potential. The calculation can reproduce the region having positive (partial derivative V-2(0)/partial derivative p)(T) values, as observed for a series of alkylbenzene derivatives. Such shape factors as the form of the tetraatomic molecule (linear, cis, and transform) and the position of larger atoms, namely, the differences between the molecule with the larger end atom and the one with the larger center atom, have been studied in their relation to the pressure dependence of V-2(0). The effects of larger atoms have been proved to be predominant. The structure of the solvation layer has been discussed on the basis of the radial distribution functions. The pressure dependence of V-2(0) was not clearly seen in the radial distribution function.