This study will assess the role of chlamydial organisms, especially Chlamydia pneumoniae, in the etiology of pneumonia as well as other respiratory syndromes by studying the prevalence, clinical symptoms, and serological response of patients in various populations. Specimens from healthy children, university students, geriatric patients, and NIH immunocompromised patients will be studied. A one milliliter portion of all bronchial alveolar lavage (BAL) specimens that are submitted to the NH Microbiology Service will be frozen at - 70 degrees C and sent to the Chlamydia laboratory at Johns Hopkins Hospital in Baltimore, Maryland, for testing. Tests to be performed include culture, ELISA, PCR, and fluorescent antibody staining. Serum from these patients will also be sent to determine serological response to chlamydia. A clinical data form will be prepared from information obtained by chart review.