This thesis was carried out on the genetic study of leukemia by studying the : chromosomal abnormalities ; pedigree analysis and protein profile for 127 cases (67 males and 60 females) of three types of leukemia ALL, AML & CML patients with various age groups ..Results of the survey showed that the incidence of leukemia was high in ages of (1-10) years and it was higher in males in females. Results of cytogenetic studies indicated that there were two types of changes : structural and numerical changes either in peripheral blood or bone marrow samples. In AML patients, karyotyping had shown that there were 13 cases of AML - M3 , which had a distinguishing chromosomal changes , t ( 15 ; 17) . In a female affected with AML another type of changes 46 , xx, t (E; ?) are detected in their peripheral blood . Also, ring chromosome was present in the cells of patient affected with AML - M5 . In 5 cases of AML (three females and two males) their metaphase showed monosomy7 , and the presence of marker chromosome in some casese study showed, the presence of Philadelphia chromosome in 24 cases of CML as the sole cytogenetic abnormality in the cells , where as , (8 cases) with no Philadelphia chromosome . Cytogenetic analysis of bone marrow samples was carried out on (43 cases) of ALL patients. Sixteen of these cases were karyotyped by using direct method . Four cases showed numerical changes with hyperdiploid counts . The results indicated that there were three cases of ph' chromosome present in the bone marrow samples of ALL patients . The results obtained from pedigree analysis for family 1, family 2 and family 3 illustrated that leukemia might have been transmitted as an autosomal dominant trait with notable vertical pattern of inheritance through the generations .However, in family 4 incomplete pentrance may be the cause of leukemia transmission through generation. The protein profile studies showed that there were differences in protein bands between normal groups and each type of leukemia groups . There was a band which present in three groups of leukemia and not present in the normal group and the expression of this band may be used as a marker in the diagnosis of leukemia . Although ,the alteration in the position or protein band may reflect the gene expression in leukemia patients . This altered protein might be an important factor in the pathogenesis of chronic & acute leukemia .