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No abstract

SUMMARY.A method is described for the estimation of free testosterone in human peripheral plasma. This method which uses the double isotope dilution derivative principle with C'*-testosterone as marker steroid, H-'-acetic anhydride as deriving agent, shows nonnal male levels to range from 0-49-0-98 ng./lOO ml. and females from less than 0-05 nfi./lOO ml. to 0-31 (iR./lOO ml. The results obtained by this method have been compared with those given by other techniques for the estimation of this steroid hormone.INTRODUCTION.