It is now possible to produce comparatively large concentrations of highly reactive metastable species in laboratory sources and to study metastable atoms and molecules with very long radiative lifetimes by photoionization mass spectroscopy, by vacuum ultraviolet absorption techniques, or by direct observation of the feeble radiation emitted by these excited species. These methods are being used widely to study the collisional deactivation of aeronomically important metastable species by quenching or by reaction. New information on radiative lifetimes, diffusion coefficients, and reaction rate coefficients is now available. These results are tabulated and reviewed in the light of atmospheric measurements and current theories of the terrestrial airglow and aurora.