The ν 6 , ν 1 7 , and ν 2 1 fundamental bands of dimethyl ether have been assigned and rotationally analyzed. The spectra used were recorded at 0.005 cm - 1 spectral resolution with a Fourier-transform spectrometer coupled to a supersonic molecular beam leading to a rotational temperature of about 70 K. The ν 6 and ν 2 1 bands do not seem to be perturbed and the analysis of the rotational structure leads to band centers located at 933.906 6(9) and 1 103.951(1) cm - 1 , respectively, and to accurate rotational and centrifugal distortion constants. For the ν 1 7 band at 2817.385(2) cm - 1 , only the P and R branches could be assigned.