AbstractSeptal neurons from embryonic rats do not survive for 24 hr when dissociated and cultured at low density in a serum‐free medium. Lamunin at 5–40 μg/ml acts as a survival‐promoting agent in the presence of 1 mM pyruvate. Laminin is effective in promoting survival only if it is added before or during cell plating; it does not support survival if added after cell attachment. Variations in laminin concentration do not effect the total number of cells attaching to the culture plate. The percentage of septal cells with neurites is increased in a dose‐dependent manner by laminin as early as 45 min after cell plating, suggesting an effect of laminin on the rate of neurite initiation. Neurite extension at 24 hr is also dependent on laminin concentration. This study suggests that some interaction between cells and the substrate, independent of cell attachment, has a profound effect on cell physiology, increasing both cell survival and the rate of neurite extension. This study also defines the survival requirements of septal neurons in a chemically defined environment in a low‐density situation where cellular interactions are at