Monitoring the incidence of acute coronary events is critical to assess the health and economic burden of coronary heart disease. This working paper uses linked data from Western Australia and New South Wales to assess the central assumptions underlying the proxy measure for estimating the incidence of acute coronary events, in the absence of a heart disease register. This validation study shows that the algorithm may underestimate the incidence of acute coronary events in Australia, but despite this the methodology does provide a reasonable measure of the acute coronary events in Australia.