The purpose of this study was to evaluate the efficacy of parasternal ultrasonography (US) in diagnosing internal mammary lymph node metastases in breast cancer, an important site of occult metastases, adversely affecting the disease-free interval and long-term survival. Thirty-five patients who were diagnosed with breast cancer were examined for internal mammarian lymph node (IMLN) involvement with parasternal US, and results were correlated with computed tomography (CT). Longitudinal and transverse images of the first through sixth parasternal rib interspaces were evaluated with a 7.5-MHz linear-array transducer. The enlarged nodes were demonstrated as discrete, spherical or ovoid hypoechoic lesions in six cases with parasternal US, and corresponding CT scans confirmed the presence of lymphadenopathy. Our results suggest that parasternal US may be helpful in the evaluation of IMLN metastases in breast cancer as a part of staging the disease.