In this prospective study 39 patients with malignant liver tumours were examined by rapid CT. CT was performed before contrast, as dynamic CT, with and without table movement and, in some patients, images were obtained four hours after contrast injection. Time/density curves of hepato-cellular carcinomas (nine cases) showed more rapid and more intense enhancement of the tumour than of the liver parenchyma, whereas tumours of biliary origin (ten cases) showed a slower and less marked enhancement than surrounding tissue. In addition, it was possible to differentiate hypovascular metastases (18 cases) and hypervascular lesions by means of the time-density curve. Best diagnostic information was obtained by dynamic bolus CT. This method without table movement is best for differentiating focal lesions, whereas dynamic CT with table movement shows the extent and number of tumour lesions.