We demonstrate a new assay in vitro using reaggregated cerebellar neurons in order to test the role of the L1 molecule in migration events. Cells other than neurons were eliminated in these cultures. Cerebellar neuron reaggregates plated on L1 molecule substrates migrated at rates similar to those observed in vivo. This migration was blocked by anti-L1 antibody. These findings suggest that this culture could provide a useful system with which to directly study relationships between neuron migration and adhesion molecules.