The excess molar volume and ultrasonic speed of (polyethers + 2-methoxyethanol) have been measured at the temperature 298.15 K as a function of composition. The polyethers were ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol diethyl ether, and diethylene glycol dibutyl ether. The ultrasonic speed values have been combined with those of the excess molar volumes converted to densities to give estimates of the product K S,m of the molar volumes and isoentropic compressibility ΞΊ S , and the excess quantity K E S,m . The excess volumes are negative over the entire range of composition for all mixtures with the exception of diethylene glycol dibutyl ether, which changes sign from positive to negative. The K E S,m values are negative for all mixtures. Comparable measurements have been carried out on the values of these two properties in an effort to assess the effects of increasing the alkyl group size with a common polar head group, and of inserting oxyethylene groups with a common alkyl group. Also, the deviations of the speed of sound u D were compared with the mixing function Ξ΄u calculated in the paper. Graphs of V E m , u D , Ξ΄u, and K E S,m against composition are presented as a basis for a qualitative discussion of the results.