The purpose of this study was to determine the interexamination agreement of ultrasound of the breasts. This includes the complete process of performing whole breast ultrasound and interpreting the dynamic scanning and the static images by one person. In a prospective study, 58 patients with a clinical indication for mammography underwent an ultrasound examination of both breasts by three independent sonographers. The sonographers had full knowledge of the physical and mammographic findings. Histology and 12 month follow-up were used as the reference standard. Interobserver variability for both mammography and breast ultrasound was measured using linearly weighted kappa statistics. Receiver operator characteristic curves were constructed to compare the diagnostic performance of the observers. The interexamination agreement for the score of the probability of malignancy after mammography was substantial (kappas ranged from 0.63 to 0.65). The interexamination agreement for the final score of the probability of malignancy after mammography and ultrasound examination was slightly better (kappas ranged from 0.72 to 0.75). The area under the receiver operating characteristic curves after mammography and ultrasound examination ranged from 0.97 to 0.98. Ultrasound examination of the whole breast shows a substantial interexamination agreement. Ultrasound examination of the breast adds consistency to mammography and physical examination.