Electrode geometry effects neglected by previous investigators are shown to be significant for electrical breakdown in vacuum for gap lengths 0 to 1 mm exhibiting breakdown at 0 to 60 kV for Al, Cu, and stainless steel electrodes. In particular, data demonstrating curvature, area, and polarity effects are reported. The effects of material transfer, particle inertia, protrusion formation, erosion, and patterned deposits are also reported.