Acute lymphoblastic leukemiae (ALL) represent about one third of all malignancies at the child age. The cases of leukemia in sucklings, together with cases of monozygote twins with genotype-identical leukemia suggest a posibility of prenatal origin of some ALL, but a direct proof of intrauterine origin may only be done by detection of clonally specific markers of leukemia cells in the newborn of fetal material.The cells of leukemia clone can be univocally characterized by clone-specific gentype changes. These changes in ALL include, among other things, clonal rearrangements of immunoglobulin genes and gene for T-cell receptors. The authors investigated, whether individual rearrangements of immunoreceptor genes may be found retrospectively in blood samples taken immediately after birth and used for a retrospective analysis of leukemia. The Guthrie cards of 23 children, who have been treated for ALL in later periods of life, were the source of newborn DNA. Identical rearrangements of immunoglobulin and/or T-receptor gene have been demonstrated in the diagnostic as well as the newborn materials in two patients.

        Key words: acute lymphoblastic leukemia, intrauterine origin, the Guthrie card, backtracking, immunoreceptor genes, the clone-specific rearrangements