Cyclophosphamide(CY)was intraperitoneally administered once a week to C57BL/10mice that had received Rous sarcoma virus(RSV)-induced S1018B10 syngeneic tumor transplantation and in whom tumor diameter exceeded 4.5 mm. Survival was prolonged in a group of mice that also received a mixture of LEM and MAK orally. When splenic cells were cultured under mitomycin C-treated S1018B10 stimulation and the S1018B10-directed cell killing ability was examined, the effector cells were found to be F4/80 - DC/Mф cells. Flow cytometric analysis showed that the proportion of F4/80- DC/Mф cells in the splenic cell culture of the CY+LEM+MAK treatment group was higher than that in the untreated group. The ratio of F4/80+ CD8a+ cells in the CY+LEM+MAK treatment group was lower than that in the untreated group.