Abstract : Quartz inclusions embedded in volcanic materials can be used for dattng Quaternary volcanoes by TL or ESR methods. For these techniques the initial zeroing by heat is assumed. However, this assumption can sometimes be questioned either because the temperature was not high, like in phreatomagmatic deposits, or because of contamination, like in thin tephra layers. Preliminary observations suggested that the présence of thé E' center could be an indicator of poor initial zeroing. This possibility was investigated in the present work. Quartz grains from various geological contexts were studied for comparison. Annealing and régénération of the E' center was explored.