Analysis of pediatric ALL samples revealed expanded CD34+CD38− population (1.3% of all mononuclear cells (MNC); healthy subjects: 0.1–0.2%), consisting of two distinct subpopulations (1): major abnormal CD34+CD38−CD19+ cell subpopulation (1.1% of MNC) and minor CD34+CD38−CD19− cell subpopulation (0.2% of MNC). This evidence concerns the gene CD34 and acute lymphoblastic leukemia.