It is shown that Titan's surface and plausible atmospheric thermal opacity sources—gaseous N 2, CH 4, and H 2, CH 4 cloud, and organic haze—are sufficient to match available Earth-based and Voyager observations of Titan's thermal emission spectrum. Dominant sources of thermal emission are the surface for wavelenghts λ ≳ 1 cm, atmospheric N 2 for 1 cm ≳ λ ≳ 200 μm,, condensed and gaseous CH 4 for 200 μm ≳ λ ≳ 20 μm, and molecular bands and organic haze for λ ≲ 20 μm. Matching computed spectra to the observed Voyager IRIS spectra at 7.3 and 52.7° emission angles yields the following abundances and locations of opacity sources: CH 4 clouds: 0.1 g cm − at a planetocentric radius of 2610–2625 km, 0.3 g cm −2 at 2590–2610 km, total 0.4 ± 0.1 g cm –2 above 2590 km; organic haze: 4 ± 2 × 10 −6, g cm, −2 above 2750 km; tropospheric H 2: 0.3 ± 0.1 mol%. This is the first quantitative estimate of the column density of condensed methane (or CH 4/C 2H 6) on Titan. Maximum transparency in the middle to far IR occurs at 19 μm where the atmospheric vertical absorption optical depth is ⋍0.6 A particle radius r ≲ 2 μ m in the upper portion of the CH 4 cloud is indicated by the apparent absence of scattering effects.