Small activated carbon particles adsorbing etoposide were injected into the proximal lymph nodes of mice and tested for therapeutic effect on distal lymph node metastases. Eight days after s.c. inoculation of 5 x 10(5) P388 leukemia cells in the left hind foot pad of mice, when metastases had been established in the secondary draining lymph nodes (lower paraaortic nodes), etoposide (5 mg/kg) was injected into the primary draining node (left popliteal node) in the form of activated carbon particles adsorbing etoposide (ETOP-CH group) or etoposide aqueous solution. After drug administration, the primary lesion was removed so that lymph node metastases were not affected by the primary lesion. Two days after drug administration, the secondary draining nodes were extirpated, and the P388 leukemia cell number in these nodes was estimated by an i.p. transference method. The estimated number of P388 leukemia cells in the lymph nodes in the ETOP-CH group was statistically significantly (by Student's t-test, P less than 0.05-0.005) less than the number of P388 leukemia cells in the other treatment groups.