The relative Raman cross sections of gases which are of interest in air pollution studies have been measured at 5145 Å. These relative differential cross sections compared to that of N2are as follows: O3(4.0), CH4(8.0), C3H8(2.4, 5.8), NO (0.55), N2O (2.7, 0.53), and H2(2.2). The absolute Raman cross section for N2has been revised to be (4.4±1.7) × 10−31cm2/sr at 5145 Å, for vertically polarized input and 90° scattered Raman radiation that is not analyzed for its polarization.