1. By using the anti-sense oligodeoxynucleotide inhibition strategy, we demonstrated that the production of CSF-1 by macrophage was blocked specifically by a CSF-1 anti-sense oligodeoxynucleotide complementary to the 5' end of the coding region of mouse CSF-1 m-RNA transcripts, but not by the CSF-1 mRNA transcripts, but not by the CSF-1 sense oligomer. 2. The LPS-induced condition medium of macrophages treated with CSF-1 anti-sense oligodeoxynucleotide retained the capacity of stimulating mouse fibroblast cells and bone marrow cells producing CSF-1 in vitro. 3. In addition to the inhibition of CSF-1 production by macrophages CSF-1 anti-sense oligodeoxynucleotide also inhibited the CSF-1 production of fibroblast cells and bone marrow cells stimulated by the macrophages conditioned medium. 4. These results suggest that macrophages stimulate their own development by mediating CSF-1 production at least in three ways: (1) production CSF-1; (2) stimulating fibroblast cells; (3) bone marrow cells to produce CSF-1. There is a positive feedback mechanism for macrophage hematopoiesis and its functional expression.