The main objective of this article is to know about aspiration pneumonia. Aspiration pneumonia is caused by bacteria that usually reside in the oral and nasal pharnyx. Traditionally, aspiration pneumonia referred to a disease caused by less virulent bacteria, primarily oral pharyngeal anaerobes. It is nowadays recognized that the numerous general communityacquired and hospital acquired pneumonias consequence from the aspiration of pathogans from the oral cavity or nasopharynx.