Twenty-five serum specimens from personnel immunized with botulinum pentavalent toxoid (ABCDE) had titers of neutralizing antibodies to type A (5.7 to 51.6 IU/ml), type B (0.75 to 18 IU/ml), and type E (0.61 to 10 IU/ml) botulinum toxins. Titers for one type could not be used to predict titers for another type in individuals receiving the toxoid. Cross-neutralizing antibodies to type F botulinum toxin were not detected (less than 0.0125 IU/ml).