Some weaknesses of our study should be noticed. First, the presence of recall bias is a possibility, as cases may recall their habits differently than controls. However, in this investigation it may have been less of an issue, due to our use of hospital controls. Next, the questionnaire used in this investigation places no particular emphasis on any specific item. Thus, there is little reason to believe that cases were more motivated than controls to recall aspirin use. Next, the use of hospital controls might introduce bias, due to the possibility that some controls were suffering from conditions that would make them more likely to use aspirin. However, greater likelihood of aspirin use in the control group would only have attenuated the true risk estimate, rather than produced spurious associations. Also, hospital controls were selected from a large pool of eligible participants with a wide variety of non-cancer diagnostic groups, minimizing bias arising from potential overrepresentation of patients with characteristics that may be associated with the exposures. Finally, the questionnaire did not assess the specific doses of analgesic preparations, such as regular or extra-strength tablets. Further, we did not have detailed information on other NSAIDs that participants may have taken and cannot rule out the possibility that cases may have been more likely to have taken preparations such as ibuprofen or prescription NSAIDs, which would have resulted in an overestimated or entirely spurious results. The strengths of this study include the large number of stomach cancer case subjects according to standardized protocols. Furthermore, we are able to adjust for major potential confounders for stomach cancer, although this changes the results only marginally.