Objective:To confirm the existence of regional differences in coronary death rates in Australia and New Zealand and to determine whether or not these are associated with parallel differences in the incidence of acute myocardial infarction.Design:Descriptive epidemiological study.Setting:Community based study.Subjects:Residents of Auckland, Newcastle and Perth aged 25–64 years admitted to hospital for acute myocardial infarction or dying from coronary heart disease between 1983 and 1987.Main outcome measures:Definite acute myocardial infarction or coronary death classified according to the criteria of the World Health Organization MONICA project.Results:This study confirms the marked variation, evident from official statistics, in mortality rates from ischaemic heart disease between Newcastle (high), Auckland and Perth (low). A different pattern is observed for the incidence of acute myocardial infarction and there are also obvious differences between centres in the case fatality ratios for all acute coronary events combined. Newcastle has the highest rate for all coronary events, particularly in women. Auckland is characterised by substantially higher case fatality ratios compared with the two Australian cities. This is due especially to higher rates of coronary death outside hospital. Perth, which has the lowest mortality rates and case fatality ratios in both men and women, has rates for admission to hospital for acute myocardial infarction and all cases of ischaemic heart disease that are disproportionately high in relation to the corresponding mortality rates.Conclusion:The differences in case fatality ratios between these three centres are not readily explained by artefacts related to enumeration or classification. Rather, they are most likely related to differences in the natural history of ischaemic heart disease in the three populations. Differences in medical management may also contribute to the substantial variation in mortality rates.