Introduction & Objective: in vitro studies shown the effect of zinc sulfate on healing of ulcers but limited in vivo studies have been done to demonstrate this effect in human. This study was conducted to investigate the effect of zinc sulfate on peptic ulcer disease Materials & Methods: This is a double blind randomized clinical trial study. We studied people who referred to endoscopy clinic in Sanandaj Besat hospital during 2002-2003. The patients were divided into two groups, case group (n=45) and control group (n=58). Only patients who had duodenal and stomach ulcer were included. All patients received standard treatment for ulcer consisting of amoxicillin, metronidazole, omeprazole and bismuth. Interventional group received one zinc sulfate capsule (220 mg) every other day. After four weeks endoscopy was performed for each patient. Data analysis was done by SPSS software using descriptive statistics, x², Fisher exact and T test. Results: There was no difference between the case and control group in factors such as place of residency, smoking, alcohol and NSAID drug consumption and ulcer size. The mean size of ulcers in case group before and after treatment were 24.65±17.72 mm and 3.8±7.3 mm while in control group were 22.51±21.22 mm and 5.7±10.8 mm, respectively. The differences were not statistically significant. Conclusion: Zinc compound could be effective in healing peptic ulcer however, more studies with higher doses of zinc are required to determine its effective dose.