The history of a patient with a suspected ischemic brain infarct undergoing an indium-111-tropolone white cell labelled test is reported. The patient, who died 12 h after injection of the labelled cells, suffered of a brain haemorrhage. The post-mortem examination has allowed for the first time the measurement of radioactivity in different organs following the injection of indium-111-labelled leucocytes. High radioactivity was found only in tissues affected by inflammatory processes and in the lymphonodes draining the corresponding areas. This report clearly indicates the importance of this method for the study of white cell localization and circulation to the sites of infections.