Three foot-and-mouth disease virus non-structural protein antibody detection kits, CHEKIT FMD-3ABC, UBI FMD NS EIA and DVIVR NSP ELISA, were compared in the study. The results showed that the specificity of the kits ranged from 96.7 to 100% in naive pigs and from 93.6 to 98.1% in vaccinated pigs, and that the DVIVR kit had the highest analytical sensitivity. The kappa statistics for the detection of 612 sera were 0.582, 0.447 and 0.658 for CHEKIT/UBI, CHEKIT/DVIVR and UBI/DVIVR, respectively. This study also revealed that measurable non-structural protein specific antibodies in some of infected pigs were sustained either for shorter periods or in intermittent patterns, thus aggravating the difficulties associated with the removal of pre-exposed pigs in the field. (C) 2003 Elsevier B.V. All rights reserved.