<正>Bystander effects on non-irradiated V79 cells were observed by irradiated conditioned medium (ICM) method and co-cultured with carbon-ion-irradiated V79 cells. In the ICM method, cells were irradiated with 1 Gy of carbon ions, cultured with new fresh medium at 37℃for 1 and 2 h. The medium was collected and filtered with 0.22 μm film to remove cells irradiated completely. This medium was transferred into culture dishes with normal cells. After cultured for 7 d, cell colonies were counted. The results were shown in Tab.1, the colony