Monoclonal antibodies (MAbs) were prepared against the putative binding domain of botulinum neurotoxin A (BoNT/A), a nontoxic 50-kDa fragment. Initially, all fusion products were screened against the holotoxin BoNT/A and against the binding fragment, BoNT/A H(C). Eleven neutralizing hybridomas were cloned, and their specific binding to BoNT/A H(C) was demonstrated by surface plasmon resonance, with dissociation constants ranging from 0.9 to <0.06 nM. Epitope mapping by real-time surface plasmon resonance showed that the antibodies bound to at least two distinct regions of the BoNT/A H(C) fragment. These MAbs will be useful tools for studying BoNT/A interactions with its receptor, and they have potential diagnostic and therapeutic applications.