Ulceration corresponds to tissue damage, breaching the muscularis mucosae. When ulcers arise in the acid-peptic environment of the gastroduodenum, they are usually termed as Peptic Ulcer Disease (PUD).Peptic ulcer is the most common ulcer of an area of the gastrointestinal tract. Peptic ulcer remains a significant public health problem; it has been estimated that 5-10% of the population is at risk of developing this disease in their lifetime, with considerable social and economic losses.The study of blood grouping is very significant as it plays an important role in genetics, blood transfusion, forensic pathology and may have some association with diseases like duodenal ulcer, diabetes mellitus, urinary tract infection. This monograph highlights the relation between ABO blood group and risk of peptic ulcer especially in Pakistani population.