The relationship between ABO blood group distribution and Peptic Ulcer Disease (PUD) has been widely evaluated in the past. But data concerning the same evaluation are very limited in Iran. This study sought to determine the distribution of ABO blood group in patients with PUD in Iranian subjects. Eighty-one patients with PUD (51 male and 30 female; mean age: 49 +/- 18 years) who attended our endoscopy section were enrolled. Blood samples were used for ABO/Rhesus (Rh) blood group antigen typing. The ABO blood group phenotype distribution in subjects was as follows: 37.1% (30/81) for group A, 23.4% (19/81) for group B, 35.6% (28/81) for group O and 4.9% (4/81) for group AB. Rh positivity was found in 63% (51/81) of patients. In local healthy population, ABO/Rh blood group distribution was 33.8, 20.7, 34.7, 8.4 and 89.6% for A, B, O, AB and Rh, respectively. AB blood group distribution in healthy population was higher than PUD (8.4 vs 4.9%). In contrast, Rh positivity of PUD in Iran is lower than healthy subjects (63 vs 89.6%). Variation in the results of studies is related to different study communities. According to these results, probably ABO/Rh blood group has an important role in patients with peptic ulceration. The functional significance of ABO blood group distribution might be associated with biological behavior of PUD. The impact of blood group on PUD may be a focus for further studies.