Excess molar enthalpies, measured at 298.15 K in a now microcalorimeter, are reported for binary mixtures of methyl tert-butyl ether with diethyl ether and dipentyl ether. Smooth representations of the results are presented, and it is shown that the Flory theory provides a good basis for the correlation of the results with data for mixtures of methyl tert-butyl ether with other di-n-alkyl ethers.