Sonography is a subjective diagnostic method which is highly dependent on the experience of the operator and the equipment quality which requires real-time adjustments. Breast screening examination currently consists of clinical examination and mammography. Breast sonography, either supplementary to mammography or independently, is indicated for the dense breast, especially in younger women. Breast sonography is especially applicable for Korean women because of the denser breast parenchyma and the approximately 10-year younger incidence rate of breast cancer of Korean women compared to western women. To avoid unnecessary breast biopsy because of the high rate of false positive lesions in breast parenchyma, which is different from other body organs such as the liver or the kidney, a quality assurance program for breast sonography is essential. The quality assurance of breast ultrasound involves quality assurance of the equipment, imaging display and acquisition of clinical images, personnel qualifications and other aspects such as unification of lexicon, guideline of diagnostic examination and reporting system; US BI-RAD reporting system, assessment items and organization, education program, medical audit, certification issues, and medicolegal issues. A breast sonographic quality assurance system should be established before a scheme to initiate governmental medical insurance for breast sonography.