Specific recognition molecules ("homing receptors") on lymphocytes are thought to direct selective entry of cells into different organs. The lectin-related cell adhesion molecule LECAM-1 has previously been supposed to mediate lymphocyte entry into peripheral lymph nodes and, partially, mesenteric nodes but not into Peyer's patches. Here we present evidence that in vivo the molecule is also implicated in homing of mouse lymphocytes to Peyer's patches and may have a more general role as homing receptor for high endothelial venules-bearing lymphoid tissue, but not for most non-lymphoid tissue.