Clavibacter michiganensis subsp. michiganensis (Cmm), causal agent of bacterial canker of tomato, has been occasionally associated with a disease of bell pepper. In 1999, necrotic, blister-like leaf lesions were found associated with one green bell pepper variety grown on three nonadjacent farms in central Michigan. Transplants used to establish the farms originated from the same greenhouse. A minimum of 18 samples were taken from each farm and Cmm was isolated from nearly all (93%). On one farm, tomato plants were growing adjacent to peppers and showed foliar and fruit symptoms of bacterial canker. The presence of polymorphic bands in rep-PCR genomic fingerprints showed that the strains associated with the pepper infection were the same in all three locations but were different from the strain associated with the tomato infection. This indicated that the pepper and tomato infections had different origins. Pathogenicity tests indicated that both pepper and tomato strains could infect either host.