In a steady-state experiment, fluorescence efficiency of the electronically excited nitrogen dioxide has been measured in the pressure range of 1–1000 mTorr and in the exciting wavelength range of 3800–5200 Å using 0.1–1.0 Å resolution. It was found to be independent of the exciting wavelength in the 4150–5200 Å range, but began to decline sharply below 4150 Å. Since the dissociation limit of the ground state NO2 giving the ground states of NO and O corresponds to 3979 Å, this early onset of “predissociation” is attributed to the utilization of the rotational energy in overcoming the dissociation threshold. Probable radiationless transitions involving the excited NO2 molecules are discussed in light of the higher resolution data on the fluorescence excitation efficiencies.