  Rotation-vibration energy levels are determined for the electronic ground
state of the acetylene molecule, $^{12}$C$_2$H$_2$, using the Measured Active
Rotational-Vibrational Energy Levels (MARVEL) technique. 37,813 measured
transitions from 61 publications are considered. The distinct components of the
spectroscopic network linking ortho and para states are considered separately.
The 20,717 ortho and 17,096 para transitions measured experimentally are used
to determine 6013 ortho and 5200 para energy levels. The MARVEL results are
compared with alternative compilations based on the use of effective
Hamiltonians.
