Langerhans cells (LCs) have to leave the epidermis to migrate into the regional lymph node (LN) after receiving immunogenic signals in contact sensitivity. There should be some molecules responsible for migration of LC in this process. In order to determine whether LN cells can generate such regulatory molecules, we made a search of such molecules in the culture supernatant of LN cells obtained from hapten-painted mice by using a modified Boyden chamber method. The molecule of LC chemotaxis appeared in the culture supernatant at 24 h after hapten painting and its production declined with time thereafter. Antibodies against both ICAM-1 and LFA-1 partially inhibited the chemotactic activity, but this was not the case with anti-TNF-alpha antibody, anti-GM-CSF antibody, fibronectin RGDS. RGES peptide or laminin. The molecule was heat labile and appeared as a molecule of 45-68 kDa on high performance liquid chromatography. Our results suggest that LN cells generate one of the chemotactic molecules of LCs, by which LC can migrate to the regional LN in contact sensitivity.