---

Abstract Background & aim: Respiratory pneumonia is a common infection which interferes with several cases. The aim of this study was to determine the incidence of B. pertussis, and Legionella pneumophila in patients diagnosed with pneumonia in Shahid Beheshti Hospital by Multiplex PCR and culture. Methods: In this experimental study, after finding patients and completing the questionnaires, 126 samples of sputum were collected from the patients. The samples were transported to the laboratory and divided in two parts. Approximately 1 ml of the samples were used for Multiplex PCR and the remainder were used for culture and Gram stain immediately. Data were analyzed using chi square tests. Results: Out of the 126 samples, 35.7 %were male, 64% were female, and the mean age was 44 years. The culture results of B.pertussis and L.pneumophila were negative. However, the results of PCR showed that L.pneumophila in 13 patients (10%) and B.pertussis in one patient (0.8%) were detected respectively. Conclusion: Due to positive results obtained in this study, the importance of pneumonia caused by these bacteria can be realized in the research area. As the PCR is one of the rapid methods for the diagnosis of pneumonia. Use of this technique can have good results in the treatment of pneumonia before wasting time. Key words: B.pertussis, L.pneumophila, PCR, Respiratory Pneumonia