Abstract: We present an accurate and reliable method for localizing a mammographic lesion by ultrasound using a simple coordinate system. It does not require special grid equipment or additional personnel. We use our system, step-by-step, on a sample patient and include appropriate image documentation. The nipple is the point of reference or “origin”. The lesion is located on ultrasound using its x and y coordinates, which are the two distances from the nipple in the horizontal and vertical axes, measured with an ordinary ruler or caliper tool. The true distance from the nipple can also easily be measured and reported. Our method is reproducible and shortens ultrasound exam times to less than 10 minutes.