Protein Kinase C (PKC) activity was measured in soluble and particulate fractions of rat individual brain cortices after in vivo treatment with two cognition enhancers: oxiracetam and alpha-glicerylphosphorylcholine. Both drugs induced an increase (+40-50%) of PKC particulate activity at 1 hr after the treatment. The effect was transient; at 5 hours PKC activity was lower than in controls. The dose response curve to oxiracetam was bell shaped, the increase of PKC being significant at 100 mg/kg. At higher doses the drug induced a decrease in enzyme activity. The increased PKC activity may be related to the cortical effects of these compounds.