Receiver operating characteristic (ROC) is one form of an objective measurement that can be used to compare newer imaging technologies against human observer performance (the ability of the expert radiologist). Use of ROC curves allows one to account for a continuum of radiologic interpretations when calculating sensitivity and specificity for an imaging modality and avoids the inaccuracies that arise from assuming that imaging findings are absolutely normal or abnormal. An ROC curve is generated by plotting sensitivity on the y axis as a function of [1-specificity] on the x axis for a continuum of diagnostic criteria. ROC curves allow visual analysis of the trade offs between the sensitivity and the specificity of a test with regard to the variable diagnostic criteria used by radiologists. Because ROC curve analysis is gaining wide acceptance in medical literature, an explanation of ROC methods with the use of simple examples is necessary to increase the knowledge and understanding of practicing radiologists.