The formation of binary complexes of sulfuric acid with hydrogen chloride, water, nitric acid, chlorine nitrate, and hydrogen peroxide has been investigated by means of ab initio calculations at the Hartree-Fock and MP2 levels of theory. The hydrogen bonds for the complexes with water, hydrogen peroxide, and nitric acid are found to be strong, whereas hydrogen chloride and chlorine nitrate form only weak complexes. For the first time, structural data for binary complexes of sulfuric acid with hydrogen chloride, nitric acid, chlorine nitrate, and hydrogen peroxide have been obtained. The geometry of the calculated sulfuric acid/water complex with the highest stability is in good agreement with the available data in the literature. The stability of the sulfuric acid complexes with hydrogen peroxide and nitric acid are indications that these gases may also take part in the nucleation process of stratospheric sulfuric acid aerosol.