Intravesical application of bacillus of Calmette-Guérin (BCG) has proved to be an effective form of treatment for some stages of bladder cancer. Infrequent, serious complications of this treatment have become apparent as its use has become more widespread. We report a case of Mycobacterium bovis mycotic abdominal aortic aneurysm and a case of M. bovis mycobacteremia that developed as complications of intravesical BCG therapy. These cases are discussed in the context of a review of reported complications of intravesical BCG therapy and a review of measures currently advocated to prevent them.