Using Australian guidelines for management of acute coronary syndromes, we investigated the proportion of high-risk patients enrolled in the Acute Coronary Syndromes Prospective Audit registry who received a coronary angiogram. A prospective nationwide multicentre registry involving 39 Australian hospitals was used. The study cohort were patients with high-risk clinical features without ST segment elevation (n = 1948) admitted from emergency departments between 1 November 2005 and 31 July 2007. Eighty nine per cent of patients with ST segment elevation myocardial infarction and only 53% of eligible patients with high-risk acute coronary syndromes with no ST elevation received a diagnostic angiogram. Increasing age was associated with lower rates of angiography; a high-risk patient at the age of ≥70 years was 19% less likely to receive an angiogram than one at the age of <70 years (risk ratio (RR) = 0.81 95% confidence interval (CI) 0.76, 0.76). Women were 26% less likely than men to receive an angiogram (RR = 0.74; 95% CI = 0.65, 0.83). The adjusted RR from the multivariate analysis suggests that a patient at the age of ≥70 years was 35% less likely to receive an angiogram than one at the age of <70 years (RR = 0.65, 95% CI = 0.60, 0.73), and that women were 13% less likely than men to receive an angiogram (RR = 0.87, 95% CI = 0.80, 0.96). Indigenous patients were as likely to access angiography as eligible non-indigenous patients (RR = 1.03, 95% CI 0.85, 1.25). There is underinvestigation of high-risk patients without ST segment elevation in Australian hospitals, particularly for women and older patients. Indigenous patients are younger and have poorer risk profiles, and represent a group that would benefit from greater investment in prevention strategies.