Objectives: This study has attempted to investigate the prevalence of Chlamydophila pneumoniae (CP) infection in patients with asthma. Methods: A total of 84 patients with stable asthma (58 males + 26 females; mean age +/- SD; 37.3 +/- 11.0 years), 22 patients with asthma exacerbation (17 males + 5 females; mean age +/- SD; 33.2 +/- 9.1 years), and 34 healthy adults (18 males + 16 females; mean age SD; 30.4 +/- 11.5 years) were included in the study. Serum and throat wash samples were obtained from all patients and healthy controls 2 times, I month apart. Micro Immuno Fluorescence method for detecting CP antibodies in serum, and polymerase chain reaction (PCR) method for detecting presence of CP infection in the throat wash samples were used. Results: The frequency of PCR positivity for CP in throat wash samples was higher in the patients with stable asthma (28.6%) than in healthy control group (11.8%) (p < 0.01). However no significant difference was found between healthy control group and asthma exacerbated group (22.7%) (p > 0.05). In addition, seroprevalences of acute and chronic CP infections were not different between patient and control groups (p > 0.05). Serological acute infection for CP was not detected among patients with positive PCR results. In contrast, although not statistically significant, serologically chronic infection for CP was detected in 3 (60%) of 5 patients with asthma exacerbation, in 18 (75%) of 24 patients with stable asthma, and 2 (50%) of 4 with healthy controls (p > 0.05). Conclusion: CP infection detected by the PCR method was more prevalent among patients with stable asthma and chronic/persistant CP infection might have an important role in asthma pathogenesis.