Laboratory experiments on chemiluminescent reactions involving atomic oxygen of pertinence to the earth's nightglow are reviewed. From simple consideration it is shown that the atomic oxygen concentration in the earth's upper atmosphere must be larger than the presently accepted value of 2 × 1011 atoms/cm3 at the peak in the atomic oxygen altitude profile. Rocket measurements of the volume emission intensity of 5577 Å radiation and laboratory measurements of the rate of its excitation by three-body atomic oxygen association indicate a peak upper atmospheric atomic oxygen concentration near 1012 atoms/cm3. The excitation of molecular oxygen emission in atomic association is a multistep process involving at least one quenchable precursor. Laboratory results are inadequate to define the excitation mechanism but a strongly temperature-dependent precursor deactivation process is required for laboratory observation to be consistent with the hypothesis that atomic association is the cause of nightglow O2 emission. Other processes are briefly discussed.