Abstract: With the increased awareness of the contribution of indirect and delayed effects (such as mutation, genomic instability) to cellular outcomes after low-dose exposures, and the availability of tools (such as the microbeam and advanced cell culture systems), many new discoveries about radiation-induced bystander effect has been achieved in the past decade. Evidence accumulated has indicated that radiation-induced bystander effect is regulated by special genes, and mediated by intercellual signal transmission pathway.