The mechanisms of periodical motor activity (MA) of gastrointestinal (GI) tract are not understand completely. It is known that the role of H3-histamine receptors (H3-HR) in the control of MA of the GI is least studied. Most investigations were done in vitro, so its important to consider the role of H3-HR in vivo. The aim of the study was to investigate the action of agonist and antagonist of H3-HR on fast MA of stomach and duodenum in dogs. The study was carried out in chronical experiments on dogs with fistulas of fundus of stomach and duodenum. By ballonographyc method we investigated the action of the agonist R-a-metylhistamine (R-a-MH, 0.2 mg/kg, iv) and antagonist thioperamide (TH, 0.07 mg/kg, iv) on th fast MA. It was established that the phase of rest in stomach was 61.8±3.36 min and in duodenum 35.16±3.45 min. The phase of work in stomach and in duodenum lasted 27.4±1.49 and 51.06±2.97 min consequently. R-a-MH evoked the lengthening the rest phase of fast MA in stomach and duodenum on 28% and on 88.65% consenquently. The phase of work was decreased in stomach on 26.4% and in duodenum on 40.7%. TH evoked the lengthening the phase of work of MA in the stomach on 236.6% and in duodenum on 123%. The phase of rest in the stomach and in the duodenum was decreased on 13.4% and 8.27, accordingly. So, H3-HR have been involved in the negative regulation of GI MA.