Antimetastatic activity of cell-wall skeleton of Propionibacterium acnes C7 (P. acnes-CWS) in C57BL/6 mice varied depending on the injection route. The kinetics of antimetastatic effect against Lewis lung carcinoma (3LL) revealed that the sooner intratumoral (it) injection of P. acnes-CWS was carried out, the better the result. However, intravenous (iv) injection of P. acnes-CWS produced the best result if P. acnes-CWS was injected at about the time when metastases began to develop in the lungs. Pretreatment with intrafootpad (ifp) injection of P. acnes-CWS inhibited primary tumor growth and subsequent pulmonary metastases especially when given 7 days before tumor inoculation into the same footpad, but tended to enhance artificial pulmonary metastases when given 7 days before iv injection of tumor cells. In contrast, pretreatment with iv injection of P. acnes-CWS enhanced spontaneous pulmonary metastases especially when given 7 days before ifp inoculation of tumor cells, but inhibited artificial pulmonary metastases when given one day or 7 days before iv injection of tumor cells. These results suggest the difficulty of treatment of tumor metastases with immunological adjuvants. In T-cell-deprived mice, it injection of P. acnes-CWS showed no antimetastatic effect against 3LL, but iv injection was still effective. This indicates that T-cells are required for the antimetastatic effect of it injection of P. acnes-CWS, but iv injection of P. acnes-CWS is able to inhibit pulmonary metastases in T-cell-deprived mice.