The incentive exists to use high collector current densities in pulsed duty homopolar generators, the current densities of interest being in the range of 15--45 MA/m2. Tests have been conducted in which current pulses of up to 0.25 MA with an equivalent pulsewidth of 0.3 s have been passed between pancake brush assemblies and fiat plate collectors with collector current densities of up to 78 MA/m2and current densities in the brush fingers of 570 MA/m2. The currents carried per brush have been a comparatively low 800 A. These tests have been successful and are providing the data necessary for the design of the all-iron-rotating homopolar pulse generators.