Background and Aims:Nosocomial infections cause considerable morbidity and mortality and pose high financial burden on healthcare systems. Although surface contact, surgical incisions, wounds and catheters are responsible for a high percentage of nosocomial infections, bacterial and fungal air contaminations in hospitals have an important role in development of hospital infections. The purpose of this study was to determine the microbial profile of air contamination in some hospital wards. Furthermore, we compared the results with cultures obtained from hospitalized patients. Materials and Methods:We performed a cross-sectional analysis at Imam Hospital, Tehran, Iran. Active (Quick Take 30 pump) and passive air samplings were performed in different wards of the hospital. Air samples were cultured to detect fungi and microorganisms. The results were compared with cultures obtained from hospitalized patients at the same time. Air microbial profiles of various wards were also compared. Results: The microbial profile of air samples showed that Micrococcus was the most common bacteria. Cladosporium was the most frequent fungi found while Aspergillus niger and Alternaria were the least frequent ones. Conclusion:In some wards, the results of blood cultures were similar to microbial profile of air samples. Thus, utilizing air purification systems and air sterilization is recommended. Our findings emphasized the role of regular monitoring of the biological risk for both patient and health care workers. The results would be useful in planning for employing appropriate strategies to reduce air burden in this hospital and other hospitals with similar conditions.