Kin discrimination provides a means for bacterial individuals to identify self from non-self, and is thus the basis and prerequisite for the competition and cooperation among bacterial cells. By kin discrimination, competitive non-self-neighbors are separated from each other or are eliminated from self-populations, whereas the kin groups perform some exclusive social behaviors, such as social movement, biofilm formation and fruiting-body morphogenesis. Kin discrimination is thus suggested to aid the co-survival of different kin groups in nature. Recently, kin discrimination is becoming a hot spot in bacteriological studies. This review summarizes recent progresses in the mechanisms for bacterial kin discrimination and interactions.