A diagnostic radiopharmaceutical comprised of iodo-azomycin galactopyranoside (IAZGP) labeled with the positron-emitting radioisotope iodine I 124 and used as an imaging agent. Iodine I 124 iodo-azomycin galactopyranoside (I-124 IAZGP) is reduced under hypoxic conditions, covalently binding to macromolecules in hypoxic cells. After incorporation into hypoxic tumor cell DNA, I-124 IAZGP can be localized and quantified using positron emission tomography (PET), allowing a quantitative assessment of hypoxic tumor burden. IAZGP appears to have a higher water solubility and faster clearance from normal tissue than traditional imidazole tracers.