Background: This project addresses an important challenge in international medicine: Pneumonia as the leading cause of death from infection in developed countries. Purpose: (A) Determine the etiology of CAP among adult hospitalized patients- especially the occurrence of mixed infections- by systematic implementation of combined conventional and new diagnostic methods. (B) Assess risk factors of CAP, such as COPD, congestive heart failure, smoking, malignancy etc., predictive of re-admittance to hospital and mortality. (C) Examine the prognostic value of potential predictors in relation to all-cause mortality in adult patients hospitalized with CAP. Design: Prospective observational study with inclusion of 270 adult patients during a 3-year period, who all required admission for pneumonia in a community hospital setting. Clinical and biochemical data was recorded longitudinally by inclusion, at stable clinical situation and after 6 weeks, and mortality and need for re-admission within 12 months. Patients were examined systematically, using modern research methods to explore relevant microbes. At all points, blood tests were sampled for clinical-chemical analysis, DNA, RNA and immunological analyses. Application: A translational research approach with the ambitions to elucidate new pathogenic mechanisms which could lead to new diagnostic tools and treatment modalities. This will possibly lead to less drug exposure and unnecessary hospitalization both of which have positive consequences for patients and medical care costs.