We studied vascular endothelial growth factor (VEGF) expression in bone marrow sections obtained from 3 healthy donors and 41 patients with acute myeloid leukemia (AML) of various French-American-British (FAB) subtypes by immunohistochemical analysis using an anti-VEGF antibody. In normal bone marrow, the anti-VEGF antibody reacted with myeloid progenitor cells and megakaryocytes but not with erythroid cells or mature granulocytic cells. High levels of VEGF were found in the bone marrow in patients with AML-M1, -M2, -M3, -M4, -M4Eo, and -M5. In these leukemias, the vast majority of myeloblasts (> 90%) expressed VEGF. By contrast, in AML-M0, the percentage of VEGF-positive blasts was lower in most cases (median, 42%), and if at all detectable, these blast cells contained only trace amounts of VEGF. In AML-M3 and -M4Eo, maturing granulocytes failed to express VEGF similar to granulocytes in normal bone marrow. In AML-M6, myeloblasts exhibited VEGF, whereas erythroid cells did not. In AML-M7, blast cells and megakaryocytes were identified as major sources of VEGF. In summary, VEGF expression in the bone marrow is restricted to certain stages of differentiation and maturation of myeloid cells and correlates with the FAB category.