The purpose of this study was to observe the enhancement of alpha particles induced transformed frequency(TF) of C,3,H,10,T 1/2 cells by phorbol myristate acetate (PMA) and active oxygen species released from polymorphonuclear neutrophile (PMN). 2 days and 30 min. after exposure to alpha particles of ,241,Am PMA or PMA stimulated human blood were added to these cell cultures. 10 days and 6 weeks later the plate efficiency (PE) and TF were determined respectively. The preliminary results obtained from 1250 dishes indicated that PMA could stimulate cell proliferation, it depended on cell densities plated and doses exposed. The enhanced trend of TF in exposed cells by PMA and PMA stimulated PMN were observed, it seemed as it the exposed cells of 0.5 Gy: their TF increased 2.1 and 2.8 fold by PMA and PMA stimulated PMN respectively.