The photoion yield spectrum of HOBr was measured over the wavelength range lambda= 108-121 nm; by using a discharge flow-photoionization mass spectrometer apparatus coupled to a synchrotron radiation source. HOBr was generated by the reaction of OH with molecular bromine. A value of(10.62+/-0.04) eV was obtained for the adiabatic ionization energy (I.E.) of HOBr from photoion thresholds, corresponding to the HOBr+((2)A") <--HOBr((1)A’) transition. The structure observed in the spectrum is discussed in terms of the available states for HOBr+, which have been determined using multiconfiguration-self-consistent field calculations. A new value for Delta H-f(0) (298)(HOBr) of-9 kcal mel(-1) is derived from I.E.(HOBr) and estimates of Delta H-f(HOBr+).