Breathing is essential to life. For breathing to happen air has to pass through the nose and back of the mouth, then through the voice box and breathing tubes from where it reaches the lung tissues. This collection of organs is sometimes referred to as the respiratory tract. It is traditionally divided into upper and lower parts. The voice box separates the upper respiratory tract from the lower respiratory tract. Since the respiratory tract is connected to the outside world it is very easy for germs to get in carried in dust or droplets of moisture in the air. Many are harmless, but some may be harmful. Germs normally live in the upper respiratory tract, but the lower respiratory tract is usually free of germs. If germs enter the lower respiratory tract then illness (lower respiratory tract infection - LRTI) may result. LRTIs are one of the most common illnesses to affect people. LRTI can occur in structurally normal lung tissues, but they are much more likely in lungs previously damaged for example by tobacco smoke (chronic obstructive airways disease – COPD). There are a number of types of LRTI such as bronchitis, pneumonia and flare-ups of COPD. They can be caused by a variety of different germs and can vary in severity from the mild and self-limiting to the life threatening requiring intensive treatment. There are many different aspects to treatment including how to make the diagnosis (because other illnesses cause similar symptoms), where the patient should be treated (home vs hospital vs intensive care), what tests to do and exactly what treatment should be given. Some may benefit from antibiotics, others may not. The exact type of antibiotic may be important. Much research is being conducted to guide the answers to these questions, but most health-care staff simply do not have the time to read all the research that is published. It is therefore important that health-care staff have access to simple summaries of what to do and what not to do when treating a patient who might have a LRTI. There is now a scientific and structured way of identifying the published research and then assessing, comparing and balancing the sometimes conflicting results of different research studies leading to a series of recommendations of what to do and what not to do, together with measures of how confident the recommendation is. This document provides a list of some 103 graded recommendations, prepared in the above way, to guide health-care staff in the management of adults with LRTI. It includes prevention as well as treatment in the community and in hospital. The aim is to cut out bad practice and replace it with the practice that is based on the best quality available evidence. The ultimate outcome should be better outcomes for patients.