The effect of local tissue injection of activated carbon particle adsorbing aclacinomycin A (ACR-CH) on the cytotoxicity in popliteal, inguinal, paraaortic, and axillary lymph nodes was investigated in mice. Aclacinomycin (0.2 mg/kg), a potent antineoplastic drug was injected subcutaneously into the footpad of mice in the form of ACR-CH or as an ACR solution. After a single injection of ACR-CH, the regional nodal cytotoxic response against mouse YAC-1 lymphoma cells was markedly increased and sustained for 7-10 days. The immune response was also increased after ACR solution but to a much lesser extent. These effects were found in popliteal, inguinal, and paraaortic lymph nodal effector cells but not in the more remote axillary nodes. Absorption of adherence cells largely abrogated the cytotoxic response. These results suggest that ACR-CH did not impair but rather stimulated nodal immunoregulatory cells. Potentially ACR-CH may enhance immune responsiveness of regional lymph nodes after subcutaneous administration while concomitantly curtailing neoplastic growth in these same lymph nodes.