Acute gingival lesions are classified as acute necrotizing ulcerative gingivitis (ANUG), primary herpetic gingivostomatitis and pericoronitis. The ANUG is an inflammatory destructive disease of the gingiva, which presents with characteristic signs and symptoms. Oral lesions are characterized by punched out, crater-like depressions at the crest of the interdental papillae, subsequently involving marginal gingiva and rarely attached gingiva. Etiological factors responsible for ANUG are divided into role of bacteria (fusospirochetal complex), local predisposing factors, and systemic predisposing factors. Diagnosis is based on clinical findings. A bacterial smear may be used to corroborate the clinical diagnosis, but it is not necessary nor definitive because, the bacterial picture is not appreciably different from the other conditions. Acute herpetic gingivostomatitis (AHG) is a viral infection of the oral mucous membrane caused by herpes simplex virus-I (HSV-I) and HSV-II.