Abstract: To investigate signal transduction between irradiated cells and unirradiated cells and its potential mechanism, unirradiated hprt+ AL cells were co-cultured with irradiated hprt- AL cells which were then killed by HAT selected medium. Results show that irradiated hprt- AL cells could transmit damage signals to unirradiated hprt+ AL cells and increase the mutation fraction at the CD59 locus. Free radical scavenger DMSO and intercellular communication inhibitor Lindane significantly increase the survival of unirradiated cells while only Lindane treatment is able to suppress the CD59 mutagenicity in unirradiated cells. These results indicate that GJIC plays an important role in the process of RIBE.