We analyzed an initial step of T cell adhesion to endothelial cells under flow conditions. An initial step in T cell-endothelial cell interactions was characterized either by a rolling phase, or by an immediate arrest without rolling. Anti-E- and P-selectin Abs inhibited T cell rolling on endothelial cells under flow conditions. The rolling velocity of T cells on endothelial cells increased after treatment of endothelial cells with anti-E- or P-selectin Abs. Also, rolling of T cells was observed on E-selectin-transfected CHO cells but not on ICAM-1-transfected CHO cells. Thus, rolling of T cells under flow condition was dependent on E-selectin as well as P-selectin expressed on endothelial cells. In contrast, neither anti-E- nor P-selectin Abs inhibited the immediate arrest of T cells on endothelial cells significantly and anti-ICAM-1 Abs also failed to inhibit the immediate arrest of T cells. Therefore, other adhesion molecules may play an important role in the immediate arrest of T cells under flow conditions. The number of CD45RA- T cells rolling on E-selectin-transfected CHO cells was much higher than that of CD45RA+ T cells.