We used a new sonographic technique, real-time contrast-enhanced harmonic sonography at low acoustic energy, to evaluate liver perfusion and liver metastases from colorectal cancer in a 73-year-old woman after chemotherapy. After 6 weeks of chemotherapy, liver metastases that had been clearly visible on conventional sonography before chemotherapy were no longer detectable on conventional sonography but were still evident on contrast-enhanced sonography. At about 6 months after initiation of chemotherapy, the lesions were all visible again on conventional sonography and had become significantly larger, although some no longer showed contrast enhancement during the arterial phase. In this case, changes in arterial perfusion over time did not parallel the response of liver metastases to chemotherapy. © 2003 Wiley Periodicals, Inc. J Clin Ultrasound 31:387391, 2003 [ABSTRACT FROM AUTHOR]