Nanosecond pulsed streamer discharge plasmas are generated by two types of nanosecond pulse generators which can output 5- and 2-ns-duration pulsed voltages, respectively. The 50-kV peaks of output voltages from nanosecond pulse generators were applied to coaxial cylindrical electrodes in atmospheric-pressure nitrogen. Based on the presented photographs, it was observed that the 2-ns pulsed discharge gave the higher streamer density. © 2006 IEEE.