Xylazine was tested on the neuromuscular transmission in anaesthetised dogs. In addition, its interactions with gallamine and tolazoline on the upper lip muscles of anaesthetised dogs have been studied. Xylazine inhibited neuromuscular transmission. Furthermore, xylazine potentiated the neuromuscular blocking action of gallamine. Pretreatment with tolazoline, prevented the depressant effect of xylazine on the neuromuscular transmission. At the same time, xylazine significantly prolonged the duration of anaesthesia caused by thiopental sodium in dogs. It could be concluded that xylazine inhibited neuromuscular transmission centrally via its action of the -2 adrenoceptors and its effect was potentiated with gallamine and prevented with tolazoline.