To correlate ultrasonographic (US), clinical, and histopathologic findings in patients with breast cancer who underwent surgery for adnexal masses evident at US. A database search yielded 54 patients with breast cancer and with adnexal masses at US and histopathologic examinations. Clinical, US, and histopathologic findings were correlated. Forty (74%) patients had benign adnexal masses, and 14 (26%) had malignant masses; three patients had both benign and malignant ovarian masses. Seven patients had primary ovarian cancer, and seven had breast metastases to the ovary. All breast metastases to the ovary were bilateral solid masses at histopathologic examination and occurred in women with stage IV breast carcinoma at the time of US. Eleven ovaries with breast metastases were solid at US. The remaining three ovaries with breast metastases had cystic components at US because of hemorrhage or coexistent benign ovarian cysts. Four of seven patients with primary ovarian carcinoma had bilateral ovarian tumors, and seven of 11 ovarian carcinomas were predominantly cystic at US. No patient with primary ovarian carcinoma had stage IV breast cancer. In this small series, half the ovarian malignancies in patients with breast cancer were primary ovarian carcinomas and half were breast metastases to the ovary. Breast metastases to the ovary most frequently are bilateral solid masses at US and are associated with stage IV disease at the time of US.