Anti-tetanus toxoid monoclonal antibodies would be useful in exploring the relationship of tetanus toxin structure to its function. Tetanus toxin fragment C has been shown to be responsible for binding to neurons via gangliosides. Eleven new and two previously derived monoclonal antibodies specific for tetanus toxin fragment C were shown to recognize five different fragment C epitopes, two of which were overlapping. Three of these epitopes participate in the binding to ganglioside G(T1b). One epitope was defined by a monoclonal antibody that did not inhibit the interaction between fragment C and ganglioside. This antibody however, was blocked from binding to fragment C by antibodies that were able to inhibit the fragment C-ganglioside interaction.