Arterial chemoembolization of liver tumors should improve regional treatment by reducing native blood flow of the whole organ and redistributing residual flow toward hypovascular masses. Plasma cisplatin pharmacokinetics and its tissue uptake and relative tumor and liver vascularity were studied during surgical placement of arterial catheters in four patients and in four patients with colorectal metastases given intraoperative arterial cisplatin (DDP, 25 mg/m2), with and without coadministration of 600 mg degradable starch microspheres (DSM). Mean (± standard deviation) filterable plasma platinum levels peaked later (2 minutes) and were significantly lower after DDP with DSM (1.23 ± 0.69 μg/ml) than after DDP alone (2.13 ± 0.43 μg/ml, P less than 0.05), with the area under the curve (AUC10–30 min) values of 15.8 ± 5.5 and 25.1 ± 3.8 μg × min/ml (P less than 0.05), respectively. No differences in urine excretion, total body clearance, or plasma protein binding of platinum were observed. Tissue biopsies were started 15 minutes after DDP administration and completed in all cases within 5 minutes. Tumor platinum concentrations were significantly higher after DDP with DSM (3.03 ± 1.60 μg/g) than after DDP alone (0.67 ± 0.49 μg/ml, P less than 0.05). Liver concentrations and tumor-liver ratios of platinum also were higher, although not significantly, after DDP with DSM. Preoperative vascularization, studied with arterial perfusion scan, influenced individual tissue drug uptake in cases given DDP alone, with the lowest tumor levels in cold masses. Very high and almost superimposable liver and tumor concentrations were measured in those receiving DDP and DSM. The latter phenomenon was irrespective of native vascularization, indicating that DSM administration induced both an increased whole-liver extraction of the drug and a redistribution of blood flow and flow-dependent tissue uptake of platinum.