An elution device has been constructed which is capable of drawing radiolabelled monoclonal antibody through a Sephadex-G chromatography column under negative pressure. Monoclonal antibodies against ovarian carcinoma and T and B lymphocytes were radioiodinated using the Chloramine-T method. Labelling efficiencies were in the range 75-85%. After passing through the chromatographic eluter no 'free' iodide was detected in the antibody samples. The apparatus was simple to use and safe to the operator.