In the course of studying a multiple-step excitation process in mercury vapor for the possible application to a three-dimensional display of data, an analysis of the fluorescence mechanism was made. A dual optical-excitation process is employed by which mercury vapor is caused to radiate at a localized region in space. The radiation is in the ultraviolet and visible portions of the spectrum. A partial analysis and pertinent literature review is presented here for the resonance absorption and reradiation of light energy by mercury vapor at room temperature.