Abstract: Primary cultures of meningeal cells from embryonic rat cerebra secrete neurite growth-inducing components into serum-free culture medium. This conditioned medium (CM) was analyzed by FPLC and immunochemical and enzymatic treatments and tested for neurite promoting activity (NPA) in a quantitative bioassay using hippocampal neurons from embryonic rat. By immunoprecipitation or specific adsorption we identified laminin (LN)-proteoglycan complexes and fibronectin (FN), respectively, as the major neurite promoting components within meningeal cell CM. The LN-proteoglycan complexes and their NPA were sensitive to chondroitinase (chondroitin ABC lyase, EC 188.8.131.52) and to a smaller extent to heparitinase (heparitin sulfate lyase, EC 184.108.40.206). Minor fractions of the total NPA in CM correlated with free LN and a putative but not yet characterized FN-proteoglycan complex.