Four hundred forty-five patients had one or more breast ultrasound examinations with equipment from six manufacturers, operating at 5, 7.5, or 10 MHz. Two hundred seven patients were examined by both automated and hand-held units. In revealing cysts and solid masses, the automated and hand-held units performed nearly identically. Of 198 patients who had screening mammograms, ultrasound evaluation revealed that 85 (43%) had cysts, while 32 (16%) had solid masses. Of the 207 patients who had diagnostic mammograms for a palpable mass, 63 (30.4%) had cysts, while an equal number had solid masses. Of 45 solid masses from both groups that were imaged and biopsied, all 15 that were malignant were palpable. No nonpalpable malignancies were found by ultrasound alone.