This work presents atmospheric density and viscosity values for methyl tert-butyl ether + heptane or octane over the whole range of compositions from (273.15 to 363.15) K. A vibrating tube densimeter is used for the density measurements, and a Cannon-Fenske viscosimeter is used for the viscosity measurements. Excess molar volumes have been calculated from the density measurements and represented with a Redlich-Kister equation. The root-mean-square deviation of the excess molar volumes from the literature values is 0.018 cm(3)center dot mol(-1). We also have represented our kinematic viscosity values with a three-body McAllister equation.