To investigate the physiological significance of hepatocyte growth factor (HGF) after transcatheter arterial chemo-embolization (TACE), we measured serum HGF levels in 23 patients who underwent angiography (n = 3) or TACE (n = 20). HGF levels increased biphasically after TACE. It rapidly increased to 10-fold higher levels immediately after heparin-injection even before embolization. Serum HGF then decreased to below 1.0 ng/ml at 6 hours after the procedure. The second peak (a 2-fold increase) appeared 1-3 days after TACE. The first increase may be due to the injection of heparin which releases HGF from the cell-surface and extracellular matrix of the liver. Patients treated to a larger extent showed higher increase in serum HGF levels, and thus the impaired hepatic HGF clearance and size of regeneration may cause second elevation of serum HGF levels. Six out of eleven patients whose serum HGF levels before TACE were more than 0.5 ng/ml died in the follow-up period whereas no patients died with serum HGF under 0.5 ng/ml. Therefore, serum HGF levels before the procedure have the potential to be a good indicator of outcome.