We analysed the expression of adhesion molecules on lymphoma cells in 13 patients with Ki-1 (CD30)-positive anaplastic large-cell lymphoma (Ki-1 ALCL; lymph nodes in 6, extranodal tumours in 6, and both lymph nodes and bone in 1). Very late activation antigen (VLA)-alpha 4 (CD49d) and Hermes lymph node homing receptor (CD44) were constantly expressed in all specimens, and intercellular adhesion molecule-1 (ICAM-1; CD54) was frequently expressed in 10 of the 14 specimens. The expressions of lymphocyte function-associated antigen-1 alpha (LFA-1 alpha; CD11a) and VLA-alpha 5 (CD49e) occurred in 5 of 14 and 4 of 14 specimens, respectively. The expression of VLA-alpha 2 (CD49b), endothelial leukocyte adhesion molecule-1, neural cell adhesion molecule (CD56) and E cadherin were always lacking. VLA-alpha 6 (CD49f) was absent in all but one specimen. The expression of VLA-alpha 5 on Ki-1 ALCL was high in subcutis-cutis but absent in lymph nodes. Furthermore, in one case, LFA-1 alpha was detected in the primary lymph node, but was absent in a metastatic bone lesion. These results suggest that the expression of ICAM-1 is partially responsible for aleukemic behaviour in Ki-1 ALCL and, moreover, that the Ki-1 ALCL cells modify their expression of adhesion molecules at each of the involved organs.