Cell-cell fusion induced by the hemagglutinin (HA) spike-glycoprotein of influenza virus has been studied extensively using transfected cells expressing the protein. The initial fusion event is the formation of a small pore connecting the two cells. Its appearance has been measured by sudden changes in capacitance by whole cell patch clamp and more recently by the sudden change in the fluorescence of a possibly potential-sensitive fluorophore. Using a new design of fluorescence video microscopy capable of capturing multiple images at differing wavelengths of light simultaneously at video rates, this fluorescence event is shown to follow exponential kinetics, with a life time, τ, of approximately 350 ms.