When discussing epidemiological data we must consider the tools of assessment and the selection of the target population. As a rule, well designed population studies give us an accurate but crude picture of what is going on. What we gain in details with a more elaborate method we often lose when we want to generalise. Population studies in Göteborg have shown that the prevalence of dyspepsia is the same among men and women in the age groups between 30–70 years. After the age of 50 dyspepsia is less common. With the methods described, it was not possible to make a clear distinction between the ulcer dyspepsia group and the non-ulcer dyspepsia group except for smoking (which was more common in the ulcer dyspepsia group).