OBJECTIVE The use of contrast-enhanced ultrasonography for imaging of renal masses was first described in 1994. Since then, many new techniques for visualization of the effect of microbubble contrast agents have been developed. In this pilot study, a small number of patients was investigated with contrast pulse sequence imaging (CPS), and the characteristics of this perfusion imaging technique were evaluated subjectively and judged against the clinical diagnosis and histology findings when available. The purpose of this pilot study was to describe CPS imaging in several cases. METHODS Eighteen patients with 20 previously identified renal masses were examined with CPS. Perfusion imaging was compared with clinical diagnosis and with histologic findings when available. RESULTS Nineteen masses were visible. Various enhancement patterns could be observed, and interpretations of CPS characteristics are described. In carcinomas, inhomogeneous enhancement patterns were observed, and areas without enhancement inside the inhomogeneous lesions corresponded to necrotic areas in histologic specimens. All simple cysts and complex benign cysts showed absence of enhancement inside or in the wall of the lesion and a regular shape. CONCLUSIONS To our knowledge, this is the first study in which the characteristics of CPS imaging of renal masses have been related to clinical diagnoses and histologic features. From the results of this pilot project, we conclude that CPS is a promising technique to determine perfusion patterns in the kidney.