Hepatic metastases were induced in nude rats by intraportal injection of 2.5-5.0 x 10(6) cells from the human colonic cancer cell line LS 174 T. Quantification of tumour burden, expressed as relative metastatic area, was performed by contrast-enhanced computed tomography (CT) scanning in vivo (n = 14), contrast enhanced CT scanning post mortem (n = 21) and computer-based area calculation (CBAC) (n = 21). To determine the false-positive contribution to the estimated tumour burden by the evaluation procedures themselves, six rats without metastases were assessed. The quantification in the three different assessment groups was in close accordance in animals with an intermediate or extensive metastatic burden, but not in rats with a minor (< 4%) tumour burden. The results indicate that contrast-enhanced CT scanning can be used in this model to quantify hepatic metastases, except in animals with few and small lesions. Furthermore, the results suggest a potential for the assessment of therapeutic response by repeated contrast-enhanced CT scanning in vivo, as well as prospects for a corresponding evaluation in man.