Lung cancer is a devastating disease with poor prognosis. The design of better therapies for lung cancer patients would be greatly aided by good mouse models that closely resemble the human disease. Unfortunately, current models for lung adenocarcinoma are inadequate due to the absence of metastases. In this study, we incorporated both K-ras and p53 missense mutations into the mouse genome and established a more faithful genetic model for human lung adenocarcinoma, the most common type of lung cancer. Mice with both mutations developed advanced lung adenocarcinomas that were highly aggressive and metastasized to multiple intrathoracic and extrathoracic sites in a pattern similar to that of human lung cancer. These mice also showed a gender difference in cancer-related death. Additionally, the presence of both mutations induced pleural mesotheliomas in 23% of these mice. This mouse model recapitulates the metastatic nature of human lung cancer and will be invaluable to further probe the molecular basis of metastatic lung cancer and for translational studies.