Upon autopsy, asbestos was found in the lungs of 7 primary lung cancer patients out of 70. These seven-patients were men over 60 years old. All of them had occupational histories of exposure to asbestos. In histological classification, 4 of the cases were adenocarcinoma and the others were squamous. Six of them were in the peripheral area. According to chest X-rays two of the patients showed lung fibrosis (asbestosis), and all of them showed pleural plaque. Thus, we concluded that ten percent of the primary lung cancer cases autopsied in our hospital might be induced by exposure to asbestos.