An ELISA was developed to measure serum concentrations of tetanus toxoid-specific immunoglobulins. The titers obtained with this assay were compatible with those obtained by the standard mouse toxin-neutralization test. Serum samples from 123 llamas were analyzed for ELISA titers to tetanus toxoid. Of the 82 vaccinated adults, 75 (91%) had titers greater than or equal to 1:50. The vaccination status and titers of weanlings and juveniles (3 to 12 months old) varied; of the 21 vaccinated, 17 (81%) had titers greater than or equal to 1:50 and 7 of 9 (78%) unvaccinated llamas had titers less than 1:50. The ELISA titers of unvaccinated llamas less than 8 weeks old (crias) were matched with the maternal titers. All crias with titers less than 1:50 had dams with titers greater than or equal to 1:50.