FasL has been shown to induce angiogenesis in vivo, however, the mechanism remains to be determined. We have previously shown that Fas ligation induces expression of chemokines such as interleukin-8 by human astrogliomas, which may partially explain the in vivo angiogenic property of FasL. Intercellular adhesion molecule (ICAM)-1 is increased in various human tumors, and is thought to be involved in the processes of metastasis and angiogenesis. We demonstrate that Fas ligation induces ICAM-1 expression at the mRNA and protein levels in human astroglioma cells. Studies using Boc-D-Fmk, a pharmacological inhibitor, show that caspase activation is required for Fas-mediated ICAM-1 induction. To study the in vivo expression of Fas and ICAM-1, human low-grade astrogliomas and glioblastoma multiforme (GBM) samples were examined by ELISA for Fas and ICAM-1. Human GBM samples express higher levels of Fas compared to normal control brain, which correlates with increased ICAM-1 expression. These findings suggest that Fas ligation on human glioma cells leads to the induction of ICAM-1 expression, which involves caspase cascade signaling pathways. © 2003 Elsevier Ireland Ltd. All rights reserved.