In this work, excess molar enthalpies, H-m(E) at 298.15 K and atmospheric pressure of methylnonafluorobutylether + alkane (hexane, octane, decane, dodecane) and ethylnonafluorobutylether + alkane (hexane, octane, decane, dodecane) are reported. Values of excess molar enthalpies were measured using a Calvet microcalorimeter. The binary experimental data were fitted using a Redlich-Kister variable-degree polynomial. The excess molar enthalpy is positive for all the mixtures. Phase separation is found in the range of 0.3 < x < 0.8 and 0.3 < x < 0.94 for the mixtures methylnonafluorobutyl ether + (decane, or dodecane), respectively. (C) 2003 Elsevier B.V. All rights reserved.