The chelating agents ethylenediaminetetraacetic acid, EDTA, and diethylenetriaminepentaacetic acid, DTPA, were both effective in removing zinc-65 from man and, in most instances, DTPA appeared to be more effective than EDTA. Considerable enhancement in urinary 65Zn excretion could be induced by both these chelating agents at relatively long time intervals following the intravenous administration of tracer doses of 65ZnCl2. Also, the chelating agents, bis 2-aminoethylethertetraacetic acid, BAETA, and ethylenediamine di-orthohydroxyphenyl acetic acid, EDDHA, were effective in increasing 65Zn excretion after prolonged time intervals following the injection of 65ZnCl2.