This report describes a remote radioiodination system which is inexpensive, easy to assemble, disposable, and capable of radioiodinating curie levels of activity safely. In addition to the safety afforded by this system, an immobilized oxidant and anion exchange resin are used to generate electrophilic iodine and remove free iodine, respectively. Reducing agents are not used and, therefore, when radioiodinating F(ab')2 fragments, degradation does not occur. In contrast, chloramine-T, sodium metabisulfite (CT/SMB) iodinations of F(ab')2 fragments resulted in products with up to 40% Fab' fragments. Radiolabeling yields (65.8% +/- 8.1%) and antibody immunoreactivity (68.8% +/- 8.0%) were not statistically different (p less than 0.001) from those obtained in remote CT/SMB iodinations. The system is currently being used to radioiodinate both IgG and F(ab')2 monoclonal antibodies with up to 450 mCi 131I for clinical radioimmunotherapy trials.