The double photoionization of HBr molecules, by synchrotron radiation in the energy range between 25 and 55 eV, has been studied in a mass spectrometric experiment. The HBr2+ and Br2+ product ions have been detected by a photoelectron-photoion-coincidence technique, while the H++Br+ formation, which follows the double ionization of HBr, has been studied by photoelectron-photoion-photoion-coincidence technique. HBr2+ ions are produced with a threshold of 32.4±0.4 eV, while the dissociative channel leading to H++Br+, shows a threshold around 33 eV. The production of H+Br2+ occurs with a threshold of 40.2±0.4 eV. These results appear to be in a fairly good agreement with earlier nonrelativistic calculations of potential energy curves and also with values indirectly obtained from experimental Auger spectra. © 2002 American Institute of Physics.