Local Bacillus Calmette-Guerin (BCG) immunotherapy is an effective and widely used treatment for superficial bladder carcinoma. Local side effects are frequent, whereas systemic side effects are rare, but more serious. We report four cases of systemic BCG reaction. Although uncommon, this infectious complication of BCG therapy should always be considered in the appropriate clinical setting. The best approach to minimize this complication is a strict compliance with precautions and a close and rigorous surveillance of this drug.