Observations with an electron microscope and with a modified field-emission microscope verify the formation of submicroscopic, whiskerlike projections on the cathode surface, thus lending additional supporting evidence for the association of electrical breakdown with field emission from such sites. Several mechanisms for the formation of whiskers are identified. The predischarge current, with which the initiation of breakdown is associated, is observed to exhibit large fluctuations in the presence of contamination on either or both electrodes, and a tentative explanation is set forth in terms of a special proliferation of small protuberances.