A retrospective cohort study of 279 Chinese fishermen in Singapore was undertaken to examine the possibility of an elevated incidence of stomach cancer. The fishermen as a group had a greater than twofold excess in stomach cancer relative to Chinese men of similar age and over the same calendar years in Singapore, but the difference was not statistically significant. On further examination it was revealed that the four stomach cancer cases were observed among the subgroup of divers. The standardized incidence ratio for the divers was 4.3, which was significantly greater than unity. There was no evidence of an increased risk for cancer of any other site (lung, nasopharynx and liver) in this cohort. Dietary factors are suggested as a possible explanation for the observation of an increased risk for stomach cancer among fishermen, but larger studies are required to test this hypothesis.