Effects of cinnamaldehyde (CA), the main component of Chinese cinnamon, which has frequently been prescribed as a remedy in Chinese medicine, on the spontaneous EEG and on the recruiting and augmenting responses in rabbits were studied. CA converted resting patterns in the EEG recorded from the frontal cortex, the hippocampus, the amygdala and the midbrain reticular formation to arousal patterns in the gallamine-paralyzed preparation with the intact brain. In the midpontine pretrigeminal transected preparation, CA also induced an arousal pattern in the electrocorticogram (ECoG). In some low cerveau isole preparations, CA converted a resting pattern in the ECoG to a sequence of low voltage fast waves. In high cerveau isole preparations, CA had no effect on the ECoG. CA, in higher doses, inhibited the recruiting response and the augmenting response. CA appeared to produce a centrally originating EEG activation through a direct or indirect excitatory action on the brainstem reticular formation.