Discussed is a deceased patient, a 54-year-old male, who was admitted to hospital with the chief complaint of motor aphasia. Computed assisted tomography in the cranium showed a massive lesion in the left brain. Further, chest X-ray showed an abnormal tumorous shadow with a pleural indentation in the left middle lung field. In spite of a negativity of cancer cells in a bronchial biopsy and a brushing, we decided that this case reflected a lung cancer with brain metastasis. However, on autopsy, the tumor in the lung histologically was determined as being an (adenocarcinoma alveolar cell type) and the brain tumor was found to be a malignant astrocytoma. We have reported on this case because a double primary neoplasm, a malignant astrocytoma and lung cancer, is rare in the literature.