Leucocyte and lymphocyte subpopulations and serum immunoglobulins were studied in 14 patients who underwent splenectomy for trauma, nine patients with an autologous replant of splenic tissue after traumatic rupture of the spleen, and 23 age- and sex-matched healthy individuals. Buffy coat cells were stained by direct or indirect immunofluorescence with goat antihuman F(ab')2 immunoglobulin (B cells), Leu-1 (T cells), Leu-2a (T suppressor cells), and Leu-3a (T helper cells). Leucocytes and lymphocyte subsets were analyzed in a cytofluorograf . After splenectomy, patients showed a marked increase in both monocytes (135%) and lymphocytes (137%), with a fourfold rise in B cells, a nearly twofold rise in T cells, a reduced T/B cell ratio, and an unchanged T helper/T suppressor cell ratio. The number of B cells was significantly related to the serum immunoglobulin M level (r = 0.807, p less than 0.001). Patients with an autologous replant had moderate monocytosis (35%) and lymphocytosis (42%), with a selective rise of B cells (60%) and T suppressor cells (75%), which led to a 50% reduction of the T helper/T suppressor cell ratio. The changes observed after splenectomy indicate the major role of the spleen in cellular homing. In patients with an autologous replant , there is a tendency for normal storage of most cells, but an altered contribution of T suppressor cells to the circulating pool.