Here we report the quantification of T cell adhesion to endothelial cells using the luminescence marker BioLite. A new application for this substance was established using a microassay for the detection of TK-1 mouse T-lymphoma cell adhesion to unstimulated or TNF alpha-stimulated eEnd.2 mouse vascular endothelioma cells. Prelabelling of TK-1 with the marker resulted in luminescence values linearly related to the number of adherent T cells. The marker was not toxic for T cells or endothelial cells nor did it interfere with the expression or function of adhesion molecules on T cells (LFA-1, VLA-4) or endothelial cells (ICAM-1, VCAM-1). When compared with established techniques to quantify T cell/endothelial cell adhesion, i.e. microscopical evaluation or isotope prelabelling of T cells, this method was found to be just as reliable and sensitive.