The available molecular parameters, fundamental frequencies, and enthalpy of formation for eight bromo- and indomethanes have been critically evaluated and recommended values selected. This information has been utilized to calculate the ideal gas thermodynamic properties. C°p, S°, H°−H°0, (G°−H°0)/T, ΔHℱ°, ΔGℱ°, and log Kℱ from 0 to 1500 K using the rigid rotor-harmonic oscillator approximation.