»Kin« discrimination is a behavior where representatives of the same species behave differentially towards »kin« than toward »nonkin«. This behavior has been mostly studied in humans and social insects. Bacteria Bacillus subtilis also exert differential behavior during swarming forming a dramatic boundary upon meeting the »nonkin« swarm and merging with »kin«. Previous studies indicated stress response and even killing between non-kin cells within the boundary. Considering these findings we hypothesized that interactions between swarms of »nonkin« strains will give rise to more frequent DNA exchange between »nonkin« swarms than between »kin« swarms. We analysed B. subtilis strains with known phylogenetic and »kin« group affiliation that were isolated from a soil microscale. We labelled each strain with a gene for antibiotic resistance (SpR or CmR) and a fluorescent marker (cfp or yfp). This enabled us to experimentally determine the frequency of horizontal gene transfer of DNA between strains by selection for transformants with two antibiotic markers. Our results show that DNA exchange is more frequent at the boundary between »nonkin« than is between »kin«, which is in accordance with the set hypothesis. Also expression of comGA-yfp, coding for the DNA uptake transporter ComGA is higher at the boundary between »nonkin« swarms. Results indicate similar concentrations of extracellular DNA (eDNA) at the meeting point of »kin« and »nonkin« swarms, application of DNase over the agar abolishes DNA exchange and strains defective in competence do not exchange DNA at the meeting point of two swarms. These results provide evidence that transformation is the mechanism responsible for the horizontal gene transfer between swarms and indicate that this evolutionary important process might also be associated with »kin« discrimination.