Four cases of Acute Necrotizing Ulcerative Gingivitis (ANUG) were reported in this paper. These cases were diagnosed as ANUG clinically, histopathologically and bacteriologically. The patients with ANUG were treated systemically and locally. Local treatments were very effective. From these findings, it was suggested that the local factors were responsible for ANUG rather than systemic factors, and that the clinical features were modified and accelerated by systemic backgrounds.
