Abstract Binary ZrF 4BaF 2, HfF 4BaF 2, and multicomponent ZrF 4 based glasses have been studied by electron spin resonance spectroscopy after liquid-nitrogen-temperature X-irradiations and room-temperature γ-ray irradiations. Polycrystalline BaF 2, ZrF 4 and HfF 4 were investigated in the same manner for comparison purposes. Isochronal anneal experiments have distinguished several resonances in the glasses which are characterized as due to F 2 − molecular ions, F 0 interstitial atoms and Zr 3+ and Hf 3+ ions. Two more signals are tentatively assigned as due to a hole trapped on several fluorine ions and a hole trapped on an oxygen impurity. In lead-containing glasses the formation of Zr 3+ is strongly inhibited, presumably due to the competitive formation of Pb + ions. However, the radiation production of Pb 3+ ions was independently observed, thus suggesting that the Pb 2+ ions may serve as traps for charge carriers of either sign. No defects were detected which could be explicitly associated with other cationic constituents, such as La 3+, Al 3+, or Li +.