This study was aimed at assessing the diagnostic value of a new intravenous contrast agent SH U 508 A (Levovist) in improving color Doppler detection of renal mass vascularity. The study included 30 patients with renal masses: 22 adenocarcinomas, 1 sarcoma, 1 leiomyosarcoma, 1 urothelioma, 1 hemorrhagic cyst and 4 angiomyolipomas. The vascularization of the renal masses was investigated by means of color Doppler US, before and after the intravenous injection of SH U 508 A (Levovist), on the basis of blood flow patterns within and around the lesions. At precontrast scanning, low color Doppler signal at the periphery or within the lesions was observed in 13/30 patients only. After contrast administration, the signal-to-noise ratio increased, which allowed the visualization of tumor vessels in 26/30 patients. In 4/30 patients only no major enhancement of tumor vessels was observed. Our experience suggests that SH U 508 A (Levovist) improves color Doppler sensitivity in depicting the tumor vessels which were missed at baseline exams and in evaluating renal vein and inferior vena cava involvement.