The involvement of cell surface gangliosides in glioma cell invasion in vitro was examined using the ganglioside-specific antibody A2B5 and Matrigel-coated 8-mu m porosity polycarbonate filters. Invasion of six cell lines derived from glial tumours of different histological grades was found to be markedly inhibited by A2B5 (50-96% inhibition) in a dose-dependent manner. Furthermore, exogenous gangliosides were found to prevent cell invasion when they were incubated with cells during the invasion assay. These results suggest that cell surface gangliosides are involved in glioma cell invasion in vitro, probably because of their adhesion-promoting action to basement membrane components.