The interaction between neoplastic as well as normal T cells and vascular endothelial cells which is mediated by adhesion molecules play a key role in their trafficking, localization and infiltration. This brief article reviews our studies on the expression of adhesion molecules on leukemic cells isolated from patients with adult T cell leukemia (ATL) and HTLV-I-infected T cell line cells and on their adhesion to human umbilical vein endothelial cells (HUVEC). Fresh ATL cells expressed lymphocyte function-associated antigen-1 (LFA-1), but the expression of very late antigen-4 (VLA-4) and sialyl-Lewis(x) (SLex) was variable. Sialyl Lewis(a) (SLea) was not detected. Cell adhesion assays using HUVEC and adhesion-blocking antibodies revealed the consistent E-selectin-mediated adhesion and variable VLA-4-mediated adhesion of ATL cells to HUVEC. The studies on HTLV-I-infected T cell lines confirmed the above data. These results, together with the detection of E-selectin expression on the endothelium of the skin infiltrated with ATL cells, indicate that E-selectin-mediated adhesion is the major pathway for the adherence of ATL cells to endothelial cells. The possible role of such adhesion in the formation of skin lesions and other clinical manifestations of ATL which result from the infiltration of leukemic cells is discussed.