Ultrasound (US) screening of breast cancer was surveyed with the results of breast screening combined with mammography (MMG), US and clinical breast examination (CBE) at Ibaraki Health Service Association. Breast cancer is common among women in their late 40s in Japan, who tend to have small and dense breasts. Our results showed that US works as well as MMG in detecting breast cancers in women in their 40s, and both modalities are compensatory. There are many reports that the combination of MMG and US is a suitable method for breast screening in Japan. A large-scale randomized control trial is now ongoing to investigate whether breast screening by both MMG and US is useful to decrease breast cancer mortality.