The distribution in the body and the circulation in the blood of autologous lymphocytes labelled with indium-III were studied in two normal subjects and two patients with Hodgkin's disease. Four hours after injection radioactivity was identified in the spleen, liver, and bone marrow. Radioactivity, followed by imaging and whole body scanning, began to appear in the lymph nodes four to 18 hours after injection, and some, though not all, lymph node groups in the body could be readily visualised. There were no differences between the normal subjects and the patients with Hodgkin's disease. The pattern of clearance of radioactivity from the blood was consistent with a normal circulation between blood and lymphoid tissues of the labelled lymphocytes. Since indium-111 stays firmly attached to the cell, it seems an ideal label for studying lymphocyte kinetics, and the use of this technique may have further clinical application.