In this report we studied the translocation of fluorescent particulate antigens to the draining lymph node, and the migration of fluorescent labeled alveolar macrophages (AM) and peritoneal macrophages (PM) in mice. The results show that intratracheally (IT) instilled particulate antigens translocate to the paracortical T cell area of the draining lymph node. When labeled AM were injected IT, they were found to migrate from the alveolar space into the paracortical T cell area of the draining lymph node. An identical localisation was found after IT injection of labeled PM. When either labeled AM, or PM were injected into the peritoneal cavity, a different migration pattern was observed. Via this route the labeled macrophages migrated to the subcapsular sinus and medulla of the draining lymph nodes. It is shown that the migrated cells are not dendritic cells (DC) present in the cell preparations. A possible role for the micro-environment of the injection site, and the significance of the specific migration pattern of AM is discussed.