Since 1992, Human Botulism Immune Globulin has been provided by the California Department of Health Services to infants with probable infant botulism, the intestinal toxemia form of human botulism. Human Botulism Immune Globulin became available in California in 1992-1997 within a randomized, controlled, double-blinded, pivotal clinical trial and subsequently became available nationwide in 1998-2003 in an open-label study until its licensure in October 2003 as BabyBIG. Thereafter, Human Botulism Immune Globulin remained available nationwide as an approved orphan-drug product. To achieve prompt neutralization of circulating botulinum toxin, the decision to treat with Human Botulism Immune Globulin has been based on clinical criteria that include a consistent history and physical findings of bulbar palsies, hypotonia, and weakness. After licensure, the charts of patients who did not have laboratory-confirmed infant botulism were reviewed to identify their actual diagnoses. The approximately 5% of 681 patients treated with Human Botulism Immune Globulin who did not have infant botulism fell into 5 categories: spinal muscular atrophy, metabolic disorders, other infectious diseases, miscellaneous, and probable infant botulism lacking laboratory confirmation.