The aim of this project is to measure the uranium concentrations in blood samples taken from control group and patient group taken from different governorates of Iraq , and measure the effect of Uranium in human chromosomes and cellular division, therefore this study was designed to investigate the effects of Uranium on the human through cytogenetic studies. The first part contains the determination of Uranium concentration in blood samples using CR _ 39 track detector. The nuclear reaction used a source of nuclear fission fragments is (n, f) obtained by the bombardment of U _ 235 with thermal neutrons from (Am _ Be) source which has flux of (5 _ 103 n cm-2 s-1). The concentrations values were calculated by a comparison with standard samples which prepared in our laboratory. The result obtained show that the higher concentration of Uranium in blood samples was (1.89 ppb) in Diala Bridge, and minimum concentration of Uranium was (0.33 ppb) in Al _ Zafraniya region. The second part contains the study of three cytogenetic parameters were employed, which were including: chromosomal aberration analysis, mitotic index assay (MI), and blastogenic index assay (BI) for studying the biological effects of Uranium. The result of this study showed that Uranium has a significant effect on the human chromosomes as represented by inducing chromosomal aberrations that include chromatid _ type aberration (gap and break chromatid), and unstable structural chromosomal aberrations such as gap, break, and ring chromosome. Also dicentric, and acentric chromosome aberrations were obtained. These aberrations were scored with significant increasing as compared with control groups.