Previous findings that necrotizing ulcerative gingivitis (NUG) is a precursor to noma or cancrum oris were confirmed by the follow-up of these clinical conditions in a study of 45 Colombian patients: necrotizing ulcerative gingivitis (NUG, n = 29), necrotizing ulcerative periodontitis (NUP, n = 7) and noma (n = 9). Patients were diagnosed at the outpatient clinic of the School of Dentistry at the University of Antioquia, at the University Hospital Saint Vincent of Paul, at the Luz Castro de Gutierrez University Hospital, at the Red Cross Hospital and at the private office of one of the authors (Jiménez L., M) in Medellín, Colombia, from 1965 until 2000. Almost all the patients came from low socioeconomic groups and presented with predisposing and/or contributing factors, such as acute herpetic gingivostomatitis, measles, and leukemia (including acute lymphoblastic and chronic lymphoid leukemia). Malnutrition and poor oral hygiene were associated with the necrotizing process and favored progression from the gingiva to deeper periodontal tissues and other structures within the oral cavity or the facial tissues. No patients had human immunodeficiency virus (HIV) or AIDS, which makes these findings different from other reports. Noma can be prevented by vaccinating children against infectious diseases, by controlling malnutrition and by improving their oral hygiene. It is arrested by mechanical lesion debridement, improving oral hygiene and antibiotic therapy. Necrotizing ulcerative gingivitis may progress in some cases to ulcerative necrotizing stomatitis, necrotizing ulcerative periodontitis, and, finally, to noma. Microbial studies among new Colombian NUG, NUP and noma patients are necessary, using bacterial culturing and identification methods and molecular techniques such as PCR for viruses and bacteria, in order to establish the exact nature of these lesions.