Matrix isolation infrared spectroscopy has been combined with MP2/aug'-cc-pVDZ calculations to characterize the 1: 1 hydrogen-bonded complexes between H2O2 and the hydrogen halides HF, HCI, and HBr. The infrared spectra of the these complexes are characterized by an intense, red-shifted H-X stretching band, as well as slight perturbations to several of the HOOH vibrational bands. For the HF complex, the intermolecular librational modes were also observed. The ab initio calculations identified two equilibrium structures on each surface, one an open structure, and the other cyclic. These two structures have similar binding energies. However, only the open structure appears to be present in argon and nitrogen matrices. This open structure is preferentially stabilized by interaction of its larger dipole moment with the matrix medium.