Pneumonia is an infection that inflames the air sacs in one or both lungs. It can cause cough with phlegm or pus, fever and chills. It mostly affects infants, young children and elderly people. A variety of organisms such as bacteria, viruses and fungi can cause pneumonia. There are several types of pneumonia such as hospital-acquired pneumonia, healthcare-acquired pneumonia, aspiration pneumonia and community-acquired pneumonia. Shortness of breath, cough, chest pain while breathing or coughing, fatigue and sweating are some of the common symptoms of pneumonia. It can be diagnosed by blood tests, chest X-ray, pulse oximetry, sputum test, CT scan and pleural fluid culture. Pneumonia can be treated through medications such as antibiotics, cough medicine and pain relievers. It can lead to breathing difficulties, fluid accumulation around the lungs, bacteria in the bloodstream, and lung abscess. Most of the topics introduced in this book cover new techniques for clinical diagnosis and treatment of pneumonia. Different approaches, evaluations, methodologies, and advanced studies on this disease have been included in it. This book will serve as a reference to a broad spectrum of readers.