The levels of the antioxidants, glutathione and ascorbate were measured in primary cultures of murine astrocytes and neurons. The concentration of glutathione (reduced, GSH + oxidized, GSSG) was high in cultured, differentiated (i.e. treated with dBcAMP) and undifferentiated (i.e. untreated) astrocytes: approximately 25 (n = 2) and 16.0 +/- 5.0 (n = 7) nmol/mg protein, respectively. In contrast, glutathione levels in neurons were low: less than or equal to 1.0 (n = 7) nmol/mg protein. Ascorbate could not be detected (less than 2 nmol/mg protein) in either cell type. The apparent lack of defense mechanisms against oxidative stress may in part account for the 'fragility' of neurons in culture. The physiological implications of glutathione compartmentation in brain are discussed.