The enthalpies of combustion of the three isomeric pentanes were measured by oxygen-bomb combustion calorimetry. The following values, based on the mass of carbon dioxide produced, are reported for the standard enthalpy of combustion ahc (298.15 Deg k)/kcal mol- 1 of these compounds in the liquid state: n-pentane, --(838.69 +/- 0.16); 2-Methylbutane, --(837.57 +/- 0.20); 2,2-Dimethylpropane, -- (834.71 +/- 0.14). These results were compared with modern values obtained by flame calorimetry. Older experimental results were reviewed, and "best values" of the enthalpies of combustion were selected. These selected values were compared with the enthalpies of combustion predicted by modern correlative procedures.