Treatment in vitro with concanavalin A was found to alter markedly the distribution of 51Cr-labeled lymph node cells to the lymphoid organs of syngeneic recipient mice. The accumulation of labeled cells in recipient spleens was greatly increased at the expense of cell migration to the lymph nodes. This effect was abrogated by addition of a competitive inhibitor of concanavalin A. The data suggest that pyranoside groups on lymphocyte membranes are associated with the homing and recirculating properties of thymus derived cells.