The effects of ethanol exposures on mitogen-activated protein kinase (MAPK) activity were determined in confluent astrocyte monolayers prepared from neonatal rat cerebral cortex. Acute 30 min exposure to 50 mM ethanol had no significant effect on MAPK activity. However, chronic exposure to ethanol for 4 days elicited a concentration-dependent increase in the basal level of this enzyme activity with no parallel increase in its protein expression. In addition, the magnitude of MAPK activation by epidermal growth factor, basic fibroblast growth factor and platelet-derived growth factor was significantly increased above corresponding control values in cells chronically exposed to ethanol. Immunolabeling experiments indicated that the protein expression of receptors for these growth factors was unaffected by ethanol treatment. Our results suggest that even after chronic ethanol treatment, MAPK phosphorylation and, hence, activation remains elevated.