AbstractYoung adult nonhuman primates were initially fed an ascorbic‐acid free diet and, subsequently, a diet with a suboptimal level of the vitamin. Following approximately 12 weeks of this dietary regime, five of seven experimental animals developed scorbutic gingivitis. 2 to 3 weeks prior to this stage, the permeability of the gingival sulcular epithelium to3Hinulin, but not to14C‐butyric acid or14C‐urea, had increased significantly (+86%, P<0.01) in the experimental group as compared to ad libitum or pair‐fed controls. This defect in the intercellular permeability barrier of the sulcular epithelium could have contributed to the pathogenesis of scorbutic gin