A flood of data indicate the importance and the relevance in both respiratory and extrapulmonary disease of Chlamydia pneumoniae infection today. Antibody prevalence rates in Western countries reach 50% in the adult population and remain high in old age suggesting a high rate of reinfection. Chlamydia pneumoniae can cause upper respiratory tract infections, like pharyngitis and sinusitis as well as bronchitis and more than 10% of community-acquired pneumonia. Recent data suggest a possible association of Chlamydia pneumoniae infection with wheezing and adult-onset asthma. However, the most intriguing hypothesis pertains the possible association between Chlamydia pneumoniae infection and atherosclerosis.A flood of data indicate the importance and the relevance in both respiratory and extrapulmonary disease of Chlamydia pneumoniae infection today. Antibody prevalence rates in Western countries reach 50% in the adult population and remain high in old age suggesting a high rate of reinfection. Chlamydia pneumoniae can cause upper respiratory tract infections, like pharyngitis and sinusitis as well as bronchitis and more than 10% of community-acquired pneumonia. Recent data suggest a possible association of Chlamydia pneumoniae infection with wheezing and adult-onset asthma. However, the most intriguing hypothesis pertains the possible association between Chlamydia pneumoniae infection and atherosclerosis.1 History of a New Agent of Pneumonia.- 2 Chlamydia pneumoniae Microbiology.- 3 Laboratory Diagnosis.- 4 Epidemiology.- 5 Pharmacological and Pharmacokinetic Basis of Chlamydia pneumoniae Treatment.- 6 Clinical Characteristics of Chlamydia pneumoniae Infection.- 7 Immunology of Chlamydia pneumoniae.- 8 Chronic Chlamydia pneumoniae Infections.- 9 Evidence for Chlamydia pneumoniae Infection in Asthma.- 10 Chlamydia pneumoniae Pneumonia: Radiological Features.- 11 Perspectives and Perceptions on the Clinical Relevance of Chlamydia pneumoniae Infection.Springer Book Archivelã#