Lightning flash parameters recorded by the National Lightning Detection Network (NLDN) were compared with those recorded by the Houston Lightning Detection and Ranging II (LDAR) network. This research focused on the relationship between the peak current and number of strokes (multiplicity) of 1047 negative lightning flashes with the spatial extent and mean altitude of the three-dimensional flashes mapped by the LDAR network. The data indicated that, for negative flashes, as the number of strokes increased so did the spatial extent of the flashes. Single-stroke flashes had mean source heights near 2 km, while flashes with higher order multiplicities had mean source heights near 8 km, and also greater horizontal extents. Low current flashes (<10kA) also had higher source heights, although that may have been due to intracloud-only flashes being incorrectly reported as cloud-to-ground flashes by the NLDN. Bipolar flashes did not have much variation in height or flash extent, with the exception of negative-first flashes, which had mean spatial extent twice that of the positive-first flashes. The flash detection efficiency of the NLDN network was 99.7% within 60 km of the network center.