Early detection of breast cancers affects the 5-year recurrence rates and treatment options for diagnosed patients, and consequently, many countries have instituted nationwide screening programs. This study compared the performance of expert radiologists from Australia and the United States in detection of breast cancer. Forty-one radiologists, 21 from Australia and 20 from the United States, reviewed 30 mammographic cases containing two-view mammograms. Twenty cases had abnormal findings and 10 cases had normal findings. Radiologists were asked to locate malignancies and assign a level of confidence. A jackknife free-response receiver operating characteristic, figure of merit (JAFROC, FOM), inferred receiver operating characteristic, area under curve (ROC, AUC), specificity, sensitivity, and location sensitivity were calculated using Ziltron software and JAFROC v4.1. A Mann-Whitney U test was used to compare the performance of Australian and U.S. radiologists. The results showed that when experience and the number of mammograms read per year were taken into account, the Australian radiologists sampled showed significantly higher sensitivity and location sensitivity (p≤0.001 ). JAFROC (FOM) and inferred ROC (AUC) analysis showed no difference between the overall performance of the two countries. ROC (AUC) and location sensitivity were higher for the Australian radiologists who read the most cases per year.