Enthalpies of evaporation of higher boiling crude oil components investigated by thermogravimetrie and differential scanning calorimetry have been compared with values estimated by means of equations of Riedel and Pitzer. The applicability of calculation methods for higher boiling components is discussed on the base of enthalpies of n-alkanes and of experimental results for crude oil and for coal liquid fractions from the literature. Enthalpies of different crude oil products are partly higher than the values of corresponding hydrocarbons. The influence of colloiddisperse phase on this result is discussed.