The BreastScreen Queensland Brisbane Southside BreastScreen Service reports on a study of 10 cases of bilateral breast carcinomas from a total cancer population of 217 cases. All cases were patients of screening examinations that were recalled for a suspicious lesion in one breast. Two cases were mammographically suspicious of bilateral tumours. In eight cases, tumours were ultrasonically visible in both breasts and in two further cases, the suspicion of bilateral malignancy was raised by the presence of bilateral microcalcification. It is not the purpose of this paper to provide a statistical analysis of the occurrence of bilateral breast cancer. This is a radiological paper from a breast screening service reporting on findings that conventional wisdom may find unusual. The incidence of bilateral breast malignancy in the study was found to be somewhat higher than expected. These cases have been diagnosed by the utilization of a particularly high standard of ultrasound and mammography, performed and interpreted by diagnosticians possessing an elevated level of suspicion of the possible presence of a second primary lesion. It is therefore proposed that an increased rate of diagnosis of bilateral tumours is possible with an evolution of assessment protocols, combined with quality ultrasound and mammography.