Learning Objectives: This course on ultrasound detection of renal mass will describe the normal variations that occur and are often confused with a mass during renal imaging. In addition, the pathology of true renal masses will also be discussed. This presentation will permit the radiologist to have a comprehension of the expected types of pathology and capabilities of ultrasound to assess the etiology of these masses. In some situations the radiologist will need to recommend cross-sectional imaging.