A five year follow-up study of a large random cohort was carried out with the aim of finding prevalence, incidence, prognosis and risk factors for upper dyspepsia according to different definitions. Fifty-four percent of the men and 47% of the women had experienced symptoms of upper dyspepsia within the past 12 months, while the prevalence of frequently occurring symptoms was 13% among men and 15% among women. Similarly the incidence was 22% among men and 25% among women, declining to 5% and 6% respectively when only frequent symptoms were considered. At five years follow-up approximately one quarter of the subjects with upper dyspepsia had recovered from all symptoms, while two thirds of the subjects who had experienced frequent symptoms did not do so any more. Psychological vulnerability increased the risk of having upper dyspepsia by 3.8, and risk of developing upper dyspepsia within five years 2.3. Different definitions identified different subjects as suffering from upper dyspepsia, and less than one quarter of the subjects fitted all the definitions.