Clostridial myositis following parenteral administration of medication is a serious complication with a high mortality. In most cases, the true nature of the disease is not suspected early, and adequate therapy is delayed. Organisms may be introduced with a needle from overlying skin that has not been adequately prepared. Medication, needle, syringe, personnel, or other fomites might harbor organisms and contaminate the procedure. Trauma from injection can set up alocus minoris resistentiaewhere circulating anaerobic organisms may colonize. Confirmation of diagnosis by needle aspiration of the area is encouraged. Thirteen cases have been previously published in the American literature; five additional cases are reported here.