Merkel cell polyomavirus (MCPyV) is an oncogenic DNA virus that causes Merkel cell carcinoma. Recently, MCPyV has been identified in other noncutaneous tumors including lung non–small cell carcinoma. However, the true role of this virus in lung carcinogenesis is unclear. We aimed to determine the efficacy of immunohistochemistry for detecting MCPyV in a series of lung adenocarcinomas. Nuclear expression of the MCPyV large T antigen was evaluated by immunohistochemistry (CM2B4 antibody) in formalin-fixed paraffin-embedded lung adenocarcinomas of different histologic subtypes. Of a total of 90 lung adenocarcinomas that were examined, none of the tumors (0%) were positive for MCPyV T antigen expression by immunohistochemistry. These data suggest that MCPyV immunohistochemistry alone might not be a sensitive method for detection of MCPyV in lung adenocarcinomas or that these tumors do not harbor MCPyV. Further studies are needed to correlate these data with molecular studies for MCPyV DNA integration and to similarly evaluate other types of lung carcinomas.