Studies of normal lymphocyte migratory properties in small animals and more recently in man using 111indium oxine labelling techniques are helping the clinician to understand the biology of tumours involving cells of the immune system. However, not enough is known about subset migration to interpret all the various patterns of dissemination observed in lymphoma patients. Such studies are important since they introduce new possibilities for therapy including the use of labelled cells to home a source a radiation preferentially to affected tissue.