Invasion of the reconstituted extracellular matrix composite, Matrigel, by eight human glioma-derived cell lines and human fetal brain cells was assessed in vitro using 8 microns polycarbonate filters in a modified Boyden migration chamber. With the exception of one low grade glioma derived cell line, all lines studied proved to be invasive while normal fetal brain cells failed to invade. This invasive potential was independent of the histological grade of the tumour from which the cell lines originated. In addition, the expression of the metastasis-associated gene 18A2/mts1 as well as the tissue inhibitor of metalloproteinases-2 (TIMP-2) was analysed in each of the glioma-derived cell lines. The 18A2/mts1 was expressed in all the cells studied with the exception of fetal brain cells and the low grade non-invasive glioma derived IPRK-7 cell line. The 18A2/mts1 related genes coding for the S100 subfamily of calcium binding proteins were found to be differentially and overexpressed in invasive cell lines. TIMP-2 was expressed only in non-invasive cell lines. These results suggest that the 18A2/mts1 and TIMP-2 genes could play an important role in the invasive behaviour of human glioma cells in vitro.