In this preliminary study, the authors studies MR imaging in four patients with malignant hepatic tumours before and after intravenous injection of 20 mumols/kg of superparamagnetic iron oxide (SIO). They obtained spin-echo sequences (SE 500/28/4, SE 2 000/28, 56/2) before and after injection and systematically compared the results with ultrasonography and computed tomography data. In every case, superparamagnetic iron oxide (SIO) resulted in a marked decrease in T2 and consequently in the signal of healthy hepatic and splenic tissue, considerably improving the visualisation of malignant lesions which remained unchanged. If the detectability of lesions is considered to depend on the contrast obtained between tumours and healthy tissue, these preliminary results are very promising.