Community acquired pneumonia is a common illness and is sometimes associated with high morbidity and mortality. Community Acquired Pneumonia (CAP) refers to an acute infection of the lung parenchyma acquired through contacts in the community and is manifested by fever, cough, chest pain, breathing difficulty and radiographic signs of consolidation of a part or parts of one or both lungs. Hemophilus influenza, staphylococcus aureus, streptococcus pneumoniae, moraxellacatarrhalis, and legionella pneumophila are the common organisms causing CAP. Lobar pneumonia and bronchopneumonia are two types of pneumonia. Chest X-ray, blood chemistry, blood cultures and respiratory specimen cultures play a very important part in the diagnosis. This chapter also comprises of well-illustrated tables on risk factors and organisms associated with community acquired pneumonia (CAP), organisms causing pneumonia in outpatients, organisms causing pneumonia in inpatients (ward), organisms causing pneumonia in inpatients (ICU) and Investigation guidelines in CAP.