Photomicrographs were made of the electrode gap between a spherical molybdenum anode and a like stainless steel cathode at voltages near the breakdown limit. At a discrete voltage for a particular gap, ionized patches of about 0.05 mm in diameter appeared on the anode surface. These ionized areas increased in luminosity and number with voltage until one or more degenerated into a highly unstable incandescent spot undergoing severe localized heating. Both of these events lead to breakdown at these sites, providing evidence for a complex vacuum breakdown process related to the prebreakdown discharges observed.