en Cell Biology Cell Biology Original Article Original Article Many biological factors affect radiosensitivity. In this study, radiosensitivity among the different blood groups was investigated. Peripheral blood sample of 95 healthy people were divided into two parts. One part was irradiated with 2 Gy Co-60 gamma rays and the second one was considered as control. Then all the samples were studied by cytokinesis-blocked micronucleus assay (CBMN assay). Our study showed that the radiosensitivity index of A+ and O+ groups was significantly higher and lower than other blood groups, respectively. It seems that blood type can be used as a radiosensitivity index for determining the given dose to radiotherapy, although extensive studies are necessary. Radiosensitivity, blood group, CBMN assay 131 135 http://ijmcmed.org/browse.php?a_code=A-10-112-1&slc_lang=en&sid=1 Farideh Elahimanesh faridehelahimanesh@yahoo.com 10031947532846003611 10031947532846003611 No Cellular & Molecular Biology Research Center (CMBRC), Babol University of Medical Sciences, Babol, Iran. Ali Shabestani Monfared monfared_ali@yahoo.com 10031947532846003612 10031947532846003612 Yes Cellular & Molecular Biology Research Center (CMBRC), Babol University of Medical Sciences, Babol, Iran. Meysam Khosravi Farsani khosravimasam@yahoo.com 10031947532846003613 10031947532846003613 No Cellular & Molecular Biology Research Center (CMBRC), Babol University of Medical Sciences, Babol, Iran. Haleh Akhavan Niaki halehakhavan@yahoo.com 10031947532846003614 10031947532846003614 No Cellular & Molecular Biology Research Center (CMBRC), Babol University of Medical Sciences, Babol, Iran. Zeinab Abedian 10031947532846003615 10031947532846003615 No Cellular & Molecular Biology Research Center (CMBRC), Babol University of Medical Sciences, Babol, Iran. Karimollah Hajian-Tilaki drhajian@yahoo.com 10031947532846003616 10031947532846003616 No Cellular & Molecular Biology Research Center (CMBRC), Babol University of Medical Sciences, Babol, Iran. Sajad Borzouisileh sajadborzouei@gmail.com 10031947532846003617 10031947532846003617 No Cellular & Molecular Biology Research Center (CMBRC), Babol University of Medical Sciences, Babol, Iran. Nayer Seyfizadeh seyfizadehn@gmail.com 10031947532846003618 10031947532846003618 No Department of Clinical Biochemistry, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran. Mehrangiz Amiri alborz812002@yahoo.com 10031947532846003619 10031947532846003619 No Cellular & Molecular Biology Research Center (CMBRC), Babol University of Medical Sciences, Babol, Iran.