Material and Methods: Seventy-two cases were assessed prospectively. The following tests were used for agent identification: (phlegm) Gram’s Stain and culture for bacteria, (serum) indirect immunofluorescent test for M. pneumoniae and Chlamydia pneumoniae, Enzyme Immuno Assay test for respiratory tract viruses, (urine) Antigen Enzyme Immune Assay test for Legionella pneumophila serogroup I antigen.

Results: The rate at which the etiologic agent was reached was found to be 77.8%. While the viruses were the most frequent infection agent (57.1%), the rate of the presence of mixed infection of other agents with viruses was 48.2%. Agents that were observed to be a single pathogen were; Influenzae A virus (6.9%), C. pneumoniae (28.6%), M. pneumoniae (25.0%), S. pneumoniae (10.7%), H. influenzae ve M. catarrhalis (7.1%), with respect to their prevalence. Mortality rate was 10.4%.

Conclusion: In addition to the high viral etiology rate, the prevalence of mixed infection is of concern. While, as the responsible agent, S. pneumoniae was lower than expected, the fact that C. pneumoniae and M. pneumoniae had higher rates suggest s the necessity of bearing in mind the atypical pneumonia agents during the treatment. The data obtained were in conformity with the results of the literature in general.