β1-Integrins (VLA-1 to -6) are cell-surface molecules binding to matrix molecules such as collagen, fibronectin and laminin. VLA-4 is the human homologue to the murine Peyer's patch homing receptor mediating cell/cell adhesion required for lymphocyte extravasation or “homing”. Other structures which have a homing-receptor function through recognition of venular endothelium are H-CAM (CD44) and LECAM-1 (LAM- 1, human MEL-14 equivalent). In order to elucidate whether these adhesion receptors are expressed in primary gastro-intestinal malignant B-cell lymphomas (GI BmL) which, in this case, might contribute to the initial confinement to this extranodal site, 31 extensively characterized tumors were examined together with reactive lymphoid tissues from small and large intestine, tonsil and lymph node using monoclonal antibodies (MAbs) against these receptors. All types of adhesion receptors were differentially expressed in the cytologically and microtopographically defined B-cell subsets [follicular center cells (FC), mantle-zone cells (MZ), extrafollicular cells (EF) and plasma cells (PC)] of the normal B-cell system. With the exception of differences in LECAM-1 levels among EF and PC of intestinal vs. nodal vs. tonsillar sites, receptor profiles were almost identical in different lymphoid organs. The expression pattern of these molecules in GI BmL was markedly heterogeneous, mimicking to some extent the receptor equipment of their reactive cellular counterpart. Thus, we failed to find a unifying adhesion receptor profile indicative of a tissue-specific homing of reactive and neoplastic B-cells.