The structure of 1,2,3,3-tetrafluorocyclopropene, C3F4, has been determined at 156 K by X-ray crystallography and in the gas phase by a combined analysis of electron-diffraction data, rotation constants derived from the microwave spectrum, and dipolar coupling constants derived froth the liquid crystal F-19 NMR spectrum. Structural parameters (distances/pm, angles/deg) for the solid at 156 K and gas phase (distances (r(g)), angles (angle(alpha))), respectively, are the following : r(C-1-C-3) = 145.3(3), 146.1(3); r(C-1=C-2) = 129.6(4), 130.7(13); r(C-3-F-6) = 137.0(2), 136.1(4); r(C-1-F-4) = 131.2(2), 131.5(3); angle C-1=C2F5 = 150.4(9), 149.9(6); angle F6C3F7 = 104.1(2), 105.4(5); angle C-1=C2C3 = 63.5(1), 63.4(3). These values are in excellent agreement with those obtained in an ab initio study of the molecular geometry at the electron-correlated MP2/TZ2P level. The dipole moment of C3F4 has been determined from Stark effect measurements to be 1.313(4) D.