We present some results of a theoretical and laboratory program to determine the thermal infrared spectral properties of the principal gaseous constituents of the atmosphere of Jupiter. G. Birnbaum has measured laboratory spectra in the 16 to 1000 um wavelength range for hydrogen and hydrogen-helium mixtures at Jovian temperatures. These are compared to theoretically computed spectra in order to determine the temperature dependence of the line strengths in the pressure-induced rotational band and the overlap parameters from the translational band. Existing spectral data for methane do not agree well with measurements of the ν 4 band at room temperature. A revised allocation of line intensities is proposed. Existing data for the ν 2 (10 um) band of ammonia do agree reasonably well with measurements at room temperature and at −77δC, but there are some important discrepancies which remain to be explained.