Expression of the macrophage colony-stimulating factor CSF-1 and its receptor, the product of the protooncogene c-fms, was detected in cell line L428, originally derived from a patient with nodular sclerosis Hodgkin's disease, and its two sublines L428KS and L428KSA. While all lines expressed membrane-associated and soluble CSF-1 proteins, L428KSA secreted 30-fold greater amounts of CSF-1 than the other cells. Three transcripts for CSF-1 (4.4, 3.7, 3.4 kilobases) were expressed in all lines and an additional 2.1-kilobase message in L428KSA. Restriction enzyme fragment analysis did not reveal any gross rearrangements of the CSF-1 gene. L428 and L428KS contained a 4.4-kilobase message for c-fms, whereas L428KSA expressed a smaller 3.8-kilobase c-fms transcript. The c-fms gene structure appeared to be unaltered in all lines by restriction enzyme fragment pattern analysis. Monoclonal anti-c-fms antibody precipitated from all cells a Mr 120,000/130,000 doublet and two lower molecular weight phosphoproteins; however, only L428KSA cells showed evidence for an autocrine growth regulation by CSF-1. DNA ploidy and proliferation kinetic studies suggested that L428KSA were derived from the actively proliferating mononuclear Hodgkin's cell population of the parental cell line. Since the simultaneous expression of CSF-1 and c-fms is a characteristic feature of mononuclear phagocytes, these results suggest that Hodgkin's cells are affiliated with the monocyte/macrophage lineage or, at least, derived from a hemopoietic cell type with the capability for aberrant expression of a monocyte-specific growth factor and its receptor.