Peptic ulcer (PU) disease is the cause of substantial morbidity and mortality in a number of countries including Australia. Despite diagnostic and treatment advances, sustained mortality from PU disease has been reported. To understand this problem a birth cohort analysis using the Median Polish Technique (MPT) was performed on 36 years of mortality data from New South Wales, Australia. The MPT allows cohort effects to be quantified, yet has rarely been applied to mortality data. Birth cohort effects detected using graphical presentation of mortality data for duodenal (DU) and gastric ulcer (GU) mortality data for both males and females, were supported by the results obtained using the MPT. The DU mortality rates for females increased significantly over the 36-year period. This increase can be explained by the presence of a birth cohort effect, with women born between 1898 and 1913 having a greater risk of dying from DU than preceding or subsequent generations. Cohort effects in GU and DU mortality data for males and in GU mortality for females were also present, although these were masked by the overall decline in PU mortality rates. The results support the findings of other studies of birth cohort effects in PU mortality data from England, Europe and Japan, and provide support for the existence of environmental factors which resulted in increased PU mortality among specific birth cohorts. Demonstration of these birth cohort effects should influence the theories of PU disease aetiology and prevention and should be considered in developing approaches for further research.