Abundance profile and stellar content of IZw18

New spectroscopic observations of the metal poor galaxy IZw 18 are discussed. Wolf-Rayet stars of WC type have been detected in the NW-HII region contrary to evolutionary synthesis model predictions. Implications on the mass loss rate and on the formation processes of WR stars are discussed. A very homogeneous metal abundance is observed within the HII region. This emphasizes the problem of the dispersal and mixing of new synthesized element in a starburst. Different scenarios are discussed, showing that metals remain most likely hidden in a hot phase and that the observed present metallicity is the result of a previous star formation event.