A Blumlein generator that has a pulsewidth of 100 nswas used to investigate the process of streamer discharge propagationin a coaxial cylindrical reactor using a streak camera. Bothpositive and negative polarities of the streamer discharges wereperformed in air at atmospheric pressure. The results showed thatthe primary and secondary streamers propagated with increasingvelocity from the central rod to the outer cylinder electrode inboth positive and negative polarities of applied voltages to the rodelectrode. The propagation velocity of the streamer heads was inthe range of 0.8–1.2 mm/ns for a positive peak applied voltage inthe range of 43–60 kV and 0.6 mm/ns for a negative peak appliedvoltage of−93 kV, respectively. The electric field at streamer onsetwas calculated to be 12 and 20 MV/m for positive and negativeapplied voltages, respectively