Abstract Though flash tubes have been used successfully as a means of locating the trajectory of charged particles the processes involved in the discharge mechanism have remained indefinite. This paper describes an investigation using cosmic ray muons as the triggering particles from which it is possible to conclude that in tubes filled with neon to a pressure of one atmosphere the number of electrons produced by the passage of the muon is sufficient to allow the transition from an electron avalanche to a streamer to take place. In the higher pressure tubes, however this is not the case, the avalanche-streamer transition occurring some time after the discharge of the tube when the free electron density has reached a sufficient level to enable streamers to develop. Further the average spacing between the streamers occurring within the flash tubes has been found to be in agreement with the results of other workers. It has also been shown that the neon metastable states have little effect on the number of free electrons present in the tube.