The kinetics of intratumoral uptake of cisplatin, carboplatin (CBDCA) and TNO-6 were studied in vitro in fragments of tumors of the head and neck maintained in culture medium under conditions simulating therapeutic conditions of chemo-embolization. Cisplatin and TNO-6 are more rapidly taken up than CBDCA (carboplatin). With each of these compounds, after 24 hours a fraction of the platinum taken up is not irreversibly bound to the tissue. The rate of uptake and the proportion of platinum irreversibly bound depends a great deal on the tumor under study. The characteristics of the diffusion indicate that TNO-6 is better used with chemo-embolization than with systemic injection. The opposite finding is seen with carboplatin. Cisplatin appears to to be about equally well-suited for either method of injection.