The expression of various cell adhesion molecules on lymphocytes and endothelial cells was examined. The strong expression of CD44 antigen on abnormal double negative T cells of lymph nodes was characteristic in MRL-lpr mice. The accumulation of abnormal double negative T cells in swelling lymph nodes was also predominant in MRL-lpr mice; this may result from augmented binding of lymphocytes to endothelial cell surfaces of lymph nodes, possibly due to the failure of Mel-14 antigen shedding from abnormal lymphocyte cell surface. The expression of VCAM-1 antigen was detected in endothelial cell surface of lymph nodes in MRL-lpr mice, which also explains the accumulation of lymphocytes in lymph nodes. However, the expression of VLA-4 antigen on lymphocytes which interact with VCAM-1 on endothelial cells was not significantly different between MRL-lpr and MRL(-)+ mice.