A nightglow emission has been seen by the Naval Research Laboratory experiment on the STP 72-1 spacecraft which appears to have the same characteristics as the N2 Lyman-Birge-Hopfield band emission reported by Huffman et al. (1980a). A seasonal variation is observed, with maximum brightness reaching several hundred Rayleighs in northern summer, and with little or no emission in southern winter. Synthesis of the spectrum given by Huffman et al. shows that the upper electronic state population peaks at vibrational quantum number v'=0, suggesting a cascade mechanism. Results from these experiments are reviewed, along with positive and negative observations from a number of other experiments. A variety of excitation mechanisms are examined. None are able to account for the various features of the Lyman-Birge-Hopfield nightglow.