The role of the lung in stomach carcinogenesis is discussed, and a revision of the Meyer hypothesis of stomach carcinogenesis is presented. According to the Meyer hypothesis, the risk for lung or stomach cancer in susceptible individuals is related to pulmonary clearance of carcinogenic particles as follows: the risk of lung cancer is decreased when particle retention in the lungs is increased and the risk of stomach cancer is increased when particle retention in the lungs is decreased. The authors suggest that the Meyer hypothesis should be modified since it ignores the role of particle deposition. They suggest that if impaired pulmonary function (obstruction) is caused by reduced airways diameter, as from increased phlegm or airways constriction, then, under obstruction, a greater proportion of larger particles may be deposited on the mucociliary blanket. Clearance from the lung would occur more rapidly due to the decreased travel distance and, thus, a potentially greater proportion of the deposited particles would be cleared to the mouth and swallowed. For example, they assert that a heavy smoker with a large exposure to dust is at increased risk of lung cancer from cigarette smoke and increased risk of stomach cancer from the dust. The effects of obstruction are to increase tracheobronchial deposition and clearance to the stomach. The Meyer hypothesis would predict an increased risk of lung cancer for both smoke and dust, and a decreased risk of stomach cancer because of reduced clearance.