Human malignant glioma cell lines are resistant to radiation-induced cell death. T98G, A172 and U87MG were irradiated with 10 Gy. 24 h, 48 h and 72 h after treatment, induction of apoptosis and necrosis was quantified by fluorescence microscopy counting the cells with apoptotic and necrotic appearance upon combined staining with Hoechst33342 and PI. The percentage of viable cells was calculated as indicated in Fig.1. Data represent means ± s.d., n = 3.