Lower respiratory infections are commonly due to viruses and are the third largest cause of death. Respiratory tract viruses have a tendency to target the specific regions in the lung and can harm the host via direct effect of the virus and the host's inflammatory response. In this study, relationships between morphologic changes in the lung and the viral agent type isolated in the lung by the polymerase chain reaction technique were investigated. This study was performed retrospectively at 113 autopsy cases in the Council of Forensic Medicine in Istanbul. Slides from the lung tissues diagnosed as interstitial pneumonia and detected viral agent in polymerase chain reaction were evaluated and reviewed under light microscope by 2 pathologists simultaneously according to predetermined bronchiolar; alveolar; and interstitial findings. Alveolar findings were detected in 108 cases (95.6%), whereas interstitial and bronchiolar findings were detected in 91 (80.5%) and 38 (33.6%) cases, respectively. Intra-alveolar edema was the most common alveolar finding. Some findings such as multinucleated syncytial cells and smudge cells can aid the search for etiologic agent. Interstitial inflammation was the most common histopathologic finding in the lung in viral infections and the most prominent clue to viral infections in the lung histopathologically without discrimination of viral agent type.