Improved infrared data have been obtained for benzene-d6 from 300—3700 cm—1 for both vapor and liquid phases. The frequencies can be interpreted very completely and satisfactorily. Good evidence was found for assigning v14 and v15 to 1287 and 838 cm—1 in benzene-d6. This provides valuable confirmation for Mair and Hornig's choice of 1310 and 1152 in benzene itself. All the fundamental frequencies for both benzene and benzene-d6 now seem to be well established, aside from small uncertainties in a few cases where the values have been inferred from combination tones or from the product rule.The infrared spectrum of benzene vapor for the range 300—700 cm—1 is also given.