Abstract
Summary 1. Distribution and excretion of radiophosphorus labelled hexafluophosphate ion has been investigated in the rat. 2. The concentration of PF6 in whole blood and plasma reached a maximum at 15 minutes, fell precipitously, and none was found 18 hours after its injection. 3. Evidence is presented that PF6 is not hydrolyzed by the rat. 4. Injected PF6 is rapidly and quantitatively excreted in the urine.