History and Objectives: Due to importance of blood groups and various reports on the prevalence of each blood group in various regions and discrepancies on the role of some blood groups on the gastrointestinal malignancies and in order to determine the prevalence of various blood groups the present study was conducted on individuals referred to the Kashan Blood Bank in 1993-1997.

Materials and Methods: The present investigation was performed in 2 steps. The first step was a descriptive study on 17287 individuals referred to the Blood bank center. Personal information, as to year to referral, sex and blood group were recorded and statistical data were presented. In the second stage is an analytical study on patients suffering from gastrointestinal malignancies hospitalized at the Shaheed Beheshti hospital in Kashan (170 patients). Final confirmation was based on the pathological findings. Patient’s records (age, sex, location of lesion, pathologic type and blood group) were listed in appropriate forms. Role of blood group on gastrointestinal malignancies were determined and relative risk was estimated.

Results: From 17287 (90.8% male, 9.2% female), O blood group was the most prevalent on blood group (35.5%). Rate of other blood groups were 28.6%, 27.7% and 8.2% for A, B and AB blood group respectively. Rh-positive carriers were 87.8% of the population. In gastrointestinal malignant patients, (170, 66.5% male, 33.5% female) and age interval of 70-79 was the most prevalent age group (55 individuals 32.4%). Gastric lesions (49.4%) were the most prevalent and esophagus, large intestine and small intestine were in lower rates. Adenocarcinoma (77%) was the most prevalent underlying cause. Blood group of 113 of patients were determined and O blood group was the most prevalent blood group among patients (39%) and B and A and AB blood groups with 31%, 28.3 and 1.7% were lower ranks respectively. 94.7% of patients had positive Rh group. B blood group (23 individuals, 38.3%) was the prevalent among gastric malignancies and the chance of occurrence is 60% compared to other blood groups.

Conclusion: Due to high prevalence of one blood group in gastric malignancy, a descriptive and analytical study with larger sample size is suggested in Kashan and other provinces.