A number of hypotheses are suggested for studying the cause of excess gastric cancers found in United States coal miners. In addition to whether the increased risk is directly related to occupation, indirect relationships such as social class, region, and other correlative lifestyle risks must be considered. The types of gastric cancers are histologically classified as diffuse or intestinal. Risk factors have been identified but actual identification of specific causes in humans has not been made. The hypotheses emphasize the relationship of increased risk to increased exposure to coal mine dust, dust in general, darkness, soil and moisture, raw tobacco juice, and nitrosamines or their precursors. Small amounts of ingested antioxidants may increase risk and may be related to lifestyle. Other hypotheses suggest that the general population has more gastric cancer and the risk in coal miners is a lag effect rather than due to specific exposures. The final hypothesis examines the possibility that a greater aggregation of high gastric risk persons are coming into coal mining. The author suggests that these hypotheses could be used to present a systematic method of studying risk factors.