Trifluorothioacetic acid-S-(trifluoromethyl)ester, CF3COSCF3, was prepared by reacting CF3C(O)Cl and AgSCF3 at 50 degrees C. The compound was characterized by C-13-, F-19-NMR, UV, and vibrational spectroscopy as well as by gas electron diffraction (GED) and quantum chemical calculations (HF, MP2, and B3LYP methods 6-31 G(d) and 6-311 +G(2df) basis sets). GED and vibrational spectroscopy result in the presence of a single conformer with C, symmetry and synperiplanar orientation of the S-CF3 bond relative to the C=O bond. This result is in agreement with quantum chemical calculations which predict the anti conformer to be higher in energy by about 4 kcal/mol. An assignment of the IR (gas) and Raman (liquid) spectra is proposed, and the GED analysis results in the following skeletal geometric parameters (r(a) and angle(a) values with 3 sigma uncertainties; these parameters are thermal averages and are not inconsistent with calculated equilibrium values): C=O = 1.202(6) angstrom, C-C = 1.525(10) angstrom, S-C(Sp(2)) = 1.774(3) angstrom, S-C(sp(3)) = 1.824 (3) angstrom. O=C-C = 118.7(21)degrees, O=C-S = 127.1(15)degrees, C-S-C = 99.8 (13)degrees.