10 normals and 37 patients with Hodgkins' and non-Hodgkin's lymphoma were examined by MRT as part of a prospective study (lumbar spine, pelvis, proximal femora). In about half the patients the MR images showed diffuse or focal areas of reduced signal intensity in the bone marrow. The observation of reduced signal areas corresponded with the pathological findings from iliac crest biopsies. To improve diagnostic accuracy, the signal intensity from a chosen region of interest was related quantitatively to a standard level.