Preliminary work has indicated that DCA inhibits disintegration of mast cell granules, which are presumably an important source of heparin. A 42-year-old Italian male with hemorrhagic manifestations and an increased titer of endogeneous heparinoid substances (20 gamma per ml. of plasma) was given 25 mg. DCA in oil I. M. daily for 4 days with a resulting sharp fall in heparinoid titer and reduction of coagulation time to normal limits. Relapse was permitted and a second course of DCA reproduced the favorable result described above.