1. The pharmacokinetics of mitomycin C (MMC) were investigated in 12 colorectal cancer patients with liver metastases undergoing chemoembolisation. Hepatic artery branches were embolized using polyvinylalcohol microspheres (150-250 microns) before applying 20 mg MMC in 4-8 min. 2. Serum MMC concentrations were determined from peripheral venous blood samples by reverse-phase HPLC using ultraviolet detection. Pharmacokinetic parameters were computed assuming an open two-compartment model. 3. Pharmacokinetic parameters were similar to values given in the literature for intravenous (IV) or intraarterial (IA) bolus MMC injections (Tmax = 7.0 min following the beginning of MMC infusion, Vss = 0.57 1/kg, C1 = 8.9 ml/min.kg, T1/2 alpha = 8.3 min, T1/2 beta = 58.6 min). 4. The area under the serum concentration-time-curve (AUC), standardized by the MMC amount injected, was similar to values reported in the literature for IV or IA bolus injections. There is no evidence for reduced systemic MMC exposure following the embolization procedure used.