The molecular beam Fourier transform microwave spectrum in the ground vibrational state of the symmetric rotor CH3-CdropC- CF3 has been detected and analyzed in the frequency interval 6-18 GHz. The molecule was generated in a pulsed dc electric discharge of trifluoropropyne and propyne seeded in neon. The observed spectrum exhibits a complex pattern of lines for each rotational transition consistent with free internal rotation of the two tops. The rotational parameters B, D-J, D-Jm, D-JK, D-JKm, and H-Jm, have been determined from the fit of the observed lines. (C) 2004 Elsevier B.V. All rights reserved.