Inflammatory exudate (SE) cells were collected from subcutaneous coverslips in mice and transferred into lethally irradiated (1,000 r) recipients. Eight days after transplantation 59Fe incorporation in the spleen and bone marrow was significantly greater than in controls treated with the suspending medium only. One hundred percent of mitoses were of the T6T6 karyotype in the marrow and spleen when SE cells were obtained from CBA/T6T6 donors. The repopulating potential of SE cells, however, lagged significantly, behind that of bone marrow cells and the failure to observe consistently macroscopic spleen colonies calls into question whether the observed regeneration was due to pluripo-tent stem cells. Radioautographic studies with 3H-TdR showed that the majority of SE cells had recently been generated, but long-lived, noncycling cells of lymphoid and monocytoid morphology were also present in the exudate.