In collaboration with three pathology departments a case-control study was conducted in the southern part of the Netherlands to investigate the risk of gastric cancer in coal miners. Between 1 January 1973 and 31 December 1983, 323 male patients were diagnosed as having a malignant neoplasm of the stomach. For each case a control was selected from the same pathology department, matched on year of birth and regardless of diagnosis. The archives of the Central Coal Miners Pension Fund were searched to obtain information about whether or not a patient had ever worked for a coal mining company in the Netherlands. Twenty two per cent of the patients had been registered as an underground coal miner, compared with 20% of the control group (odds ratio of 1.14, 95% confidence interval: 0.33-1.73). Those with gastric cancer who had ever worked underground in a coal mine did so for an average period of 16.9 years compared with an average of 19.7 years in the control group. The study gives no indication that the underground workers of the Dutch coal mines had a raised risk of developing a malignant neoplasm of the stomach.