An indirect sandwich ELISA is used by the World Reference Laboratory for Foot-and-Mouth Disease for the diagnosis of foot-and-mouth disease virus and swine vesicular disease virus. The potential for supplying ELISA 'kits' for diagnosis to other laboratories has been assessed by evaluating the reactivity of (a) immunoplates pre-coated with rabbit antisera to FMDV and SVDV and (b) freeze-dried diluted reference antisera. Immunoplates pre-coated using a sodium carbonate/hydrogen carbonate buffer retained 100% sensitivity at temperatures of 4 degrees C and -20 degrees C over the experimental storage period of 140 days but elevated storage temperatures, 18-24 degrees C and 37 degrees C, produced declining reactivity. There was a marked improvement in retention of reactivity upon storage at 37 degrees C when employing an alternative coating buffer, ammonium hydrogen carbonate. The reactivity of the rabbit antisera diluted in sodium carbonate/hydrogen carbonate solution and freeze-dried was high, as was the freeze-dried guinea pig antisera which had been diluted in each of the test solutions investigated. ELISA 'kits' for diagnosis, therefore, could be supplied using pre-coated immunoplates, with freeze-dried antiserum reagents or a combination of the two.