A modified technique of fluorescent histochemistry induced by glyoxylic acid was used to study the changes of catecholamine (CA) and 5-hydroxytryptamine (5-HT) in the brains, walls of the brain vessels and the dura mater of the rats at regular intervals after ligation of bilateral common carotid arteries (BCCA). At the same time the effect of chinese herbs, Radix Salviae Miltorrhixae, red flower and Motherwort on CA and 5-HT of these rats was also observed. In the normal rats, yellow fluorescent granules that indicated the presence of 5-HT were found in the walls of the cerebrum, brainstem, cerebellum and dura mater vessels. Green fluorescent fibers that indicated the presence of CA were clearly revealed to follow the walls of vessels of the dura mater, but not those of the brain vessels. After ligation of BCCA, the 5-HT granules of the walls of the brain vessels and the CA fibers of dura mater vessels decreased, but CA fibers occurred in the walls of the brain arteries. The above mentioned changes became more marked following prolonged of ischemia of the brain 24 hours after ligation of BCCA, very few 5-HT granules and CA fibers were found in the walls of the brain and dura mater vessels. It was interesting to see that the increase of CA fibers occurred in the whole muscle layer of the brain arteries. The changes of the monoamines were not so evident in those rats treated with Radix Salviae Miltorrhixae, red flower and motherwort even though they had also ligation of BCCA.