Abstract. The examination of 144 white mature male rats of mixed population was conducted. Experimental rheumatoid arthritis model was used to study the impact of some ACE inhibitors: omeprazole, cytotek and combinations of omeprazole with ACE inhibitors and cytotek on frequency of erosive ulcerous injuries of gastric mucosa when administered within 5 and 10 days with indometacin. Drugs were administered per os in the form of water suspension.It was established that the combined use of ACE inhibitors, omeprazole and cytotek with indometacin decreases the noci-influence of indometacin on gastric mucosa. Captopril is the most treatment medication among ACE inhibitors. Combined application of ACE inhibitors with omeprazole and cytotek increases the medicine efficacy. Com-bined use of omeprazole and captopril or omeprazole and cytotek is the most effective for prevention of side effect of indometacin on mucosa of gastroduodenal zone.