Under a variety of conditions, mouse neuroblastoma C1300 cells growing in culture differentiate to a nerve-like or "neurite" form. The role of membrane lipids in this process is being studied. Changes in the physical properties of the membranes upon differentiation have been detected by means of spin labels. When mouse neuroblastoma cells differentiate to the neurite form their membranes can no longer be induced to undergo lipid peroxidation. Lipid analyses of these cells are currently being performed in order to understand the mechanisms underlying these changes in neuroblastoma membranes.