The authors studied the hemodynamics of 5-FU hepatoarterial infusion in a colorectal cancer patient with multiple liver metastases, who had chronic renal failure maintained by hemodialysis. Under weekly high dose 5-FU hepatoarterial infusion (1,000 mg/m2, 5 hours), on a non-dialysis day, serum 5-FU concentration was 1,090 ng/ml just after the 5 h infusion, 391 ng/ml at 15 min, 217 ng/ml at 30 min, 47 ng/ml at 60 min, and < 4 ng/ml at 120 min after infusion. On a dialysis day it was 1,500 ng/ml just after infusion, 41 ng/ml at 15 min, 5 ng/ml at 30 min, and < 4 ng/ml at 60 and 120 min after infusion. A control group (n = 4), who had liver metastases from colorectal cancers and normal renal functions, showed 5-FU serum concentration of 987 +/- 384 ng/ml just after infusion, 226 +/- 117 ng/ml at 15 min, 18.5 +/- 5.8 ng/ml at 30 min, < 4 ng/ml at 60 and 120 min after infusion. The serum 5-FU concentration of the patient was maintained higher on non-dialysis days, while it decreased more rapidly on dialysis days than that of the control group. There were no clinical complications due to the weekly high dose 5-FU hepatoarterial infusion. Under the treatment of continuous 5-FU hepatoarterial infusion (500 mg/day), the serum 5-FU concentration of this patient was kept under 115 ng/ml. After hemodialysis, the concentration decreased. The serum 5-FU concentration of the control group (n = 4) was under 66 ng/ml. There were no side effects under the protocol of continuous 5-FU hepatoarterial infusion. 5-FU hepatoarterial infusion for liver metastasis was a safe treatment for a renal failure patient with hemodialysis.