The elevation of circulating hepatocyte growth factor (HGF) concentrations is associated with tumor progression and prognosis in cancer patients. We aimed to clarify whether peripheral blood mononuclear cells (PBMC) of cancer patients can produce circulating HGF. In sera and PBMC supematants of 39 cancer patients and 55 control subjects, we measured HGF concentrations by enzyme-linked immunosorbent assay and analyzed HGF expression in PBMC by reverse transcriptase-polymerase chain reaction and Western blotting. Compared with primary cancer patients and control subjects, recurrent cancer patients showed higher serum HGF concentrations (p < 0.05, p < 0.01 respectively), higher HGF concentrations in PBMC supernatants (p < 0.01 for both) and more frequent HGF mRNA expression in PBMC. Additionally, HGF mRNA was induced in PBMC of a control subject cultured with the sera of recurrent cancer patients. These results indicate that PBMC of recurrent cancer patients can produce HGF and that their sera may contain substances that induce HGF mRNA expression.