Spleen cells from mice immunized against a methylcholanthrene induced rhabdomyosarcoma inhibited tumour cell colony formation in vitro and prevented tumour development in vivo in an adoptive transfer test. Treatment of the immune spleen cells with anti-mouse immunoglobulin serum or passage through a nylon wool column, both of which reduced the percentage of immunoglobulin bearing cells in the population to less than 3-4%, did not alter their anti-tumour effects. In contrast, treatment of the spleen cells with anti-BAomicron serum abolished their anti-tumour effects both in vitro and in vivo. These results indicate that T cells are the mediators of tumour immunity in this chemically induced tumour system
