The quantity of water, lipid and some metals was measured in autopsy specimens of 8 normal livers, 9 livers with fatty change, and in 12 livers with metastases of various origins. These parameters contribute to the CT number measured in the liver. Water played a major role in demonstration of liver metastases as a low-density area on CT. Other contributory factors include iron, magnesium and zinc. Lipid and calcium had no influence in this respect. Heavy accumulation of calcium in a metastatic lesion gives a high-density area on CT. However, even when a metastatic lesion was perceived on CT as a low-density area, the calcium content of the lesion was not always lower than that of the non-tumour region.