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The anharmonic nature of the $\nu 2$ bending vibration of $C3$ has a large influence on the thermal functions of this molecule. The thermal functions based on four different models of this bending vibration are considered along with mass spectrometric data of $C3$ collected both in our laboratory and in other laboratories. The thermal functions reported by Chase et al. $(1986)1$ are selected as giving the best second and third law enthalpy of formation. The selected enthalpy of formation for $C3$ is $\Delta Hf,0=814\pm 14$ or $\Delta Hf,298=823\pm 14$ kJ/mol. The effects of the different models of the bending vibration on the enthalpy of formation will be presented.