Background: Different definitions of dyspepsia are applied by researchers yet measurement of the influence of these on prevalence estimates is uncertain. Despite continued debate regarding dyspepsia subgroups, few studies have used a data-drive approach to assess the existence and relevance of symptom clusters. We aimed to address both these issues. Methods: A random population sample (n = 2300) identified in New South Wales. Prevalence estimates of dyspepsia were calculated by applying four standardized dyspepsia definitions. Principal components analyses, using firstly the presence/absence of symptoms and then secondly severity of symptoms, were undertaken to determine if symptom factors existed. Results: Prevalence estimates ranged from 11% to 36%. Similar prevalence rates for men and women were observed for all definitions except Rome II. Over one-third of respondents nominated heartburn or epigastric pain as their most bothersome symptom. However, 22% of respondents were unable to answer this question. The principal components analysis produced four symptom factors: a nausea factor, dysmotility-like dyspepsia (early satiety and fullness), ulcer-like (epigastric pain and bloating) and reflux-like (heartburn and acid regurgitation). However, the factors accounted for less than 50% of the variance. Similar factors were identified in men and women for dysmotility-like and reflux-like dyspepsia. Use of presence/absence or severity of symptoms made little difference to the symptom factors produced or the amount of variance explained. Conclusions: The prevalence of dyspepsia depends on the definition applied. While there is some empirical evidence of symptom subgroups, they appear to be of little clinical utility.