This is a study of the accuracy of combined breast imaging (mammography and ultrasound) in young women with breast symptoms. We performed an appraisal of the literature, and improved our study design by avoiding biases identified in published work. Our study presents the sensitivity and specificity of mammography and breast ultrasound, individually and in combination, using different thresholds for categorizing test results, in a population of consecutive women. We show that combining the two imaging tests does improve sensitivity without significantly reducing test specificity. However, the number of additional cancers correctly identified using combined imaging, relative to the number of false positives, is highly dependent on breast cancer prevalence.