[en] Electron track brightness and localization are studied using three-component mixtures in a streamer chamber. The additives used are CH₄ (0.2-2%) and water vapour (0.005-0.3%). The experiments are carried out with a 180-mm-diam. and 60-mm-discharge gap glass chamber. The chamber is pumped out down to 2 x 10^-3 torr. The maximum high-voltage pulse amplitude has been 280 kV with a leading edge of about 10 ns and a pulse-decay time of 1.5 mcsec. The total instrumental pulse delay from the moment of pulse passage has been 0.4 mcsec. Pictures of electron tracks in a 32.5 kV/cm electric field are given. It has been found that there is good track localization only at pressures of 600-700 torr. The chamber storage time, 1 mcsec, allows one to work with large ionized particle fluxes, 10⁵ - 10⁶ C^-1. The size of the localized brightly shining part of the streamers along the adge does not exceed 2 mm. The optimum concentration of water vapour has turned out to be 0.05%