Despite undergoing an apparently curative surgery, over 50% of colorectal cancer patients will die within 5 years, the majority within the first 2 years from disseminated disease. Occult liver metastases are reported to be present in approximately 30% of patients and they predominantly determine the likelihood of dying from disseminated disease. The question is how to detect these occult hepatic metastases. This article reviews some of the alternative techniques, such as dynamic scintigraphy, functional computerized tomography, and duplex colour Doppler sonography (DCDS), which have been developed to predict which patients harbor these occult metastases. More recently, DCDS measurements of the Doppler perfusion index (DPI: ratio of hepatic arterial to total liver blood flow) have been shown to be highly accurate in the detection of these occult liver metastases. In addition, irrespective of Dukes stage, patients with abnormal DPI were shown to have a very poor outcome while for those with normal DPI, the prognosis was excellent. If the data are reproduced, the administration of adjuvant chemotherapy should be based on DPI status rather than Dukes stage.