Acetylene, C2H2, plays an important role in the photochemistry of the atmospheres of the giant planets, in part because of its strong absorption features in the 145--201 nm region where there is significant solar flux. Accurate photoabsorption cross section data at the temperatures of planetary atmospheres are required for interpretation of observations and for reliable photochemical models. We have measured the photoabsorption cross sections of acetylene at 195 and 295 K in the wavelength range 147--201 nm. (The 295 K measurements extend to 137 nm.) The high-resolution spectrometers employed had instrumental bandwidths smaller than those used in previous measurements and therefore produced cross sections that are less influenced by instrumental effects. Our results indicate that hot bands make small but significant contributions to the room temperature absorption spectrum of C2H2. Photochemical models of planetary atmospheres should employ cross sections measured at the temperatures of these atmospheres. ¿ American Geophysical Union 1991