Technetium 99m macroaggregated albumin (Tc-MAA) perfusion scintigraphy has been performed during hepatic arterial infusion chemotherapy using implantable reservoir. A total of 40 radionuclide (RI) studies were performed on 25 patients with liver metastasis of colorectal origin. Of 40 RI studies, 12 (30%) showed impaired liver perfusion. Three studies showed no perfusion of the liver, 3 increased radiotracer accumulations at liver hilus, 2 extrahepatic distributions, 2 catheter occlusions, 1 extravasation and 1 unilobar distribution. The accumulation of Tc-MAA in the tumor was graded from Grade I (tumor uptake decreased or similar relative to liver) to Grade III (tumor uptake remarkably increased). The response to chemotherapy was evaluable in 14 cases. A case with Grade I resulted in NC. Of 6 cases with Grade II, 1 resulted in MR, 3 in NC and 1 in PD. Of 8 cases with Grade III, 2 resulted in PR, 1 in MR and 5 in NC. Tumor response was observed in cases showing increased uptake of Tc-MAA. SPECT was performed in 7 cases, and revealed that hepatic tumors were hypervascular. We concluded that RI examination reveals not only hepatic perfusion, but also tumor microcirculation.