The accuracy of spin lattice relaxation time (T1) measurement obtained with a low field strength magnetic resonance imager for the detection of spread of malignant lymphoma to the liver was assessed. The results of histological examination obtained at open liver biopsy were compared with liver T1 values in 27 patients with lymphoma. The normal range for T1 was established by scanning 61 healthy volunteers. Magnetic resonance imaging was highly sensitive in detecting hepatic lymphoma, all seven patients with liver lymphoma proved by biopsy having considerably higher T1 values. Specificity was less good. Five out of 20 patients with no histological evidence of hepatic lymphoma had abnormal T1 values. this level of sensitivity is considerably better than that reported for other imaging methods and contrasts with the results of one previous study using a different magnetic resonance system. Low field strength magnetic resonance imaging may prove to be a useful screening test in patients with lymphoma. The presence of a normal liver T1 seems to be a reliable guide to the absence of hepatic disease.