We assessed splenic activity after splenectomy by interference phase microscopical examination of circulating red cells. Normal eusplenic children had a low number (less than 1 per cent) of red cells with surface indentations or "pits". About 20 per cent of red cells of children who had electively been subjected to splenectomy for hematologic indications were "pitted". Thriteen of 22 children who had had emergency splenectomy because of traumatic injury had a low percentage of "pitted" red cells, suggesting a return of splenic function. In five of these children a 99mTc sulfur colloid scan demonstrated multiple nodules of recurrent splenic tissue. In contrast to the prevailing opinion that splenosis is rare, we have found it to be a frequent occurrence. Return of splenic function may, in part, account for the low frequency with which overwhelming bacterial sepsis and meningitis have been documented after splenectomy for traumatic indications.