The mRNA amounts of the main nucleoside transporters (NT) and intracellular metabolizing enzymes (ME), hENT1, hENT2 (SLC29A2), hCNT1 (SLC28A1), hCNT2 (SLC28A2), hCNT3 (SLC28A3), DCK and cN-II (NT5C2), were measured in 50 pediatric leukemia cases by RQ-PCR. The gene discussed is SLC28A1; the disease is leukemia.