In this study, using immunohistochemistry, we analysed the ATRX expression status in a large series of gliomas in order to evaluate 1) the predictive potential of ATRX for IDH1/2 and H3F3A mutations and LOH 1p/19q status, 2) the optimal interobserver-reliant cut-off point for ATRX loss. The gene discussed is H3-3A; the disease is glioma.