Adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) and its counter-receptor, lymphocyte function associated antigen-1 (LFA-1), play very important roles in immune responses. In this study, the effects of cytokines on cultured human melanoma cells (MMG2) were examined, especially focussing on the expression of ICAM-1 on MMG2 and lymphocyte adhesion to MMG2. Both the expression of ICAM-1 and HLA-DR on MMG2 increased after treatment with IFN-gamma. ICAM-1 expression began to increase earlier than HLA-DR expression. TNF-alpha and IL-1 beta also increased the expression of ICAM-1 on MMG2. However, these cytokines did not increase the expression of HLA-DR. IFN-gamma had a dose dependent effect on lymphocyte adhesion to MMG2. Pretreatment of IFN-gamma treated MMG2 with 84H10 (anti-ICAM-1 antibody) or pretreatment of lymphocytes with either SPV-L7 (anti-LFA-1 alpha antibody) or IOT10 (anti-LFA-1 beta antibody) inhibited the lymphocyte adhesion to MMG2. These results suggest that ICAM-1 molecules induced on melanoma cells by IFN-gamma can interact with LFA-1 molecules on lymphocytes.