The present study was conducted to reveal the effect of the nonsteroidal anti-oestrogen toremifene on the expression of cell-surface molecules involved in the immunogenicity of tumours or the sensitivity of tumour cells to apoptotic cell death. We studied the effect of toremifene on the expression of HLA-DR, ICAM-1, costimulatory molecules CD80 and CD86, and the tumour necrosis factor receptor (TNF-R) family molecules CD27, CD30, CD40, TNF-R1, TNF-R2 and Fas (CD95) on MCF-7 breast cancer and Jurkat T cells. In addition, the effect of toremifene on Fas-mediated apoptosis was studied. Toremifene did not affect Fas expression or Fas-mediated apoptosis in Fas-resistant MCF-7 or Fas-sensitive Jurkat cells, but was found to increase the expression of ICAM-1 in both cell lines. In addition, toremifene increased the expression of CD40 and CD80 on MCF-7 cells. The expression of ICAM-1 in tumours plays an important role in the interaction of tumour cells and effector cells of the immune system. Therefore, we suggest that toremifene may modulate the immunogenicity of tumour cells by increasing the expression of ICAM-1.