This article presents data demonstrating frequent BAALC hyperexpression, also in combination with WT1 hyperexpression, in children and adults with acute myeloid leukemia (AML). Treatment included allogeneic hematopoietic stem cell transplantation. The analysis of serial measurements of BAALC and WT1 expression level in 50 AML patients (37 adults and 13 children) showed that the increased BAALC expression is more common in patients with M1, M2, M4, and M5 FAB variants of AML with equal frequency in adults and children. Furthermore, the increased BAALC expression was rather common in combination with the increased WT1 expression, which predicted poorer prognosis. Since BAALC expression level in AML patients is closely related to AML-producing progenitor cells of leukemia hematopoiesis, a serial study of this phenomenon offers insights into the role of these cells in emergence and development of post-transplantation relapses, which is of both theoretical and practical importance.