Blast cell populations of forty nine individuals with acute myeloblastic leukemia (AML) were investigated for constitutive expression of genes for various hematopoietic growth factors. Fifteen samples constitutively exhibited messenger (m) RNA for colony stimulating factor for granulocytes (G-CSF). Eleven AML specimens produced mRNA specific for CSF for granulocyte and macrophages (GM-CSF). When probed for CSF for macrophages (M-CSF or CSF-1) specific hybridization signals became detectable in six samples. Five out of six blast cell populations transcribing M-CSF, synthesized G-, and GM-CSF mRNA's simultaneously, whereas another five leukemias transcribed G-, and GM-CSF genes exclusively. Furthermore, when specific bioassays were performed to detect secretion of biologically active CSF proteins by these leukemic blast samples, twelve out of fifteen G-CSF mRNA producing cell populations, eight out of eleven GM-CSF mRNA producing cell populations and one out of six M-CSF mRNA synthesizing samples, demonstrated release of the respective, functionally active CSF's into their culture supernatants. Our results show that gene transcription and protein secretion of hematopoietic growth factors are features that are frequently detected in leukemic myeloid blast cells and involve G-, GM-, and M-CSF. With respect to recent findings of receptiveness of leukemic colony forming cells (L-CFC) for proliferative stimuli provided by various hematopoietic growth factors, our findings point out a potential role of autocrineously produced CSF's in the pathophysiology of autonomous proliferation in AML.