Calorimetric molar enthalpies of vaporization Delta(l)(g)H(m) for five alkyl-substituted pentanes were determined over the temperature range (298.15 to 368.15) K with a typical uncertainty of 0.2 per cent. The measured values, as well as corresponding calculated cohesive and internal energies, were correlated as a function of temperature by using several empirical multiparameter equations. All the equations fitted well with the data, and some of them were used to extrapolate the data toward the triple and critical boiling temperatures, and to predict the corresponding property values.