The influence of blood group types on development of brain tumors is unclear since there are conflicting reportsfrom surveys regarding the distribution of ABO blood groups and primary intracranial neoplasms. The presentdescriptive, retrospective study was therefore made of 907 patients with reliable records for ABO blood groups andproven histological diagnosis who were hospitalized with brain tumors at the Shariati Hospital neurosurgical center,between 1980 and2002. The distribution of the ABO blood groups in this study population was compared with thatin the general population by the chi-square test. Data analysis showed that there are no significant differences betweentypes of intracranial tumors and frequencies of four major blood groups. The distribution of the ABO blood groupsin patients did not differ significantly from that of the general population. Of our patients with craniopharyngioma,however, significantly more were in group A (P<0.05) compared with the general population of Iran.