The triatomic, inorganic free radical of unknown structure, HIF, is characterized by ab initio correlated many-body theory. The calculations show that HIF has a bond angle of 137.5±3°, bond lengths R(HI) = 1.64±0.5 Å and R(IF) = 2.04±0.5 Å, and a ground state of 2A′ symmetry. The computed dissociation energy for the process HIF→IF+H is 25 kcal/mole, while the experimental value is 30. The bonding in HIF is very similar to a noncollinear superposition of the two diatomic molecules HI and IF. Correlated calculations for IF, HI, HF, and the electron affinity of F are also reported. The accuracy of the dissociation energy in HIF directly parallels the accuracy of the F electron affinity.