We report a case of severe recurrent erysipelas of the breast due to infection with Streptococcus agalactiae and demonstrate that strains isolated from the skin were closely related to strains isolated from the vagina, which is consistent with the claim that the vagina acts as a reservoir for S. agalactiae isolates that are responsible for erysipelas relapse. Hypervirulence of strains and persistence of a bacterial reservoir may explain why 5 months of prophylaxis with penicillin V (1 million U daily) was necessary to achieve permanent eradication of vaginal carriage and to prevent recurrence of erysipelas caused by S. agalactiae infection.