PEP-CH is comprised of activated carbon particles that adsorb peplomycin. Mice which were inoculated with 5 x 10(5) MH 134 tumor cells subcutaneously opposite the foot-pad of the left hind paw on day 0, received a subcutaneous injection of peplomycin, 0.25 mg/mouse, in the form of PEP-CH or a peplomycin aqueous solution administered at the foot-pad of the left hind paw on day 10. The left popliteal lymph nodes then were transferred intraperitoneally to normal mice on day 14. In the PEP-CH group, the survival time of the recipients was statistically and significantly long, and the transferred tumor cell number, estimated with a calibration curve, was markedly small when compare to mice in the other treatment groups.