An analysis of the extra cellular matrix (ECM) in regionally heterogeneous midbrain glia has been started. Immunoreactivity to laminin has been tested in confluent glial cultures from lateral (L) and medial (M) sectors of 14 days mouse embryos (E14) and in neurone-glia cocultures kept for 48 hours after plating of E14 midbrain freshly-dissociated neurones. Laminin is present in both types of glial cultures, but its distribution assumes a punctate pattern in glia that is not permissive for neurite growth (M-glia) and a fibrillar configuration in a favourable glial substrate (L-glia). Moreover, laminin expression is dramatically upregulated in co-cultures although fibrillar and punctate patterns are maintained.