Molar excess enthalpies H-E of the liquid mixture propan-1-ol + methyl-t-butylether (MTBE) + 2,2,4-trimethylpentane (i-octane) have been measured by flow calorimetry including the three binary systems. The values obtained are endothermic in the whole range of ternary composition. The results can be explained by the strong hydrogen bonds existing between the alcohol molecules which are broken upon mixing. Also, cross-association between propan-1-ol and MTBE plays a significant role, The ERAS-model has been used for describing the experimental results. The model parameters adjusted to the three binary systems provide equilibrium constants and association enthalpies for the cross-association between propan-1-ol and MTBE. Results predicted by the ERAS-model in the ternary mixture describe the experiments in a satisfying way without adjusting ternary parameters.