The liquid-phase blocking ELISA (LPBE) and a specific isotype assay (SIA) modified for caprine/ovine IgG1 and IgG2 were used to detect antibodies against foot-and-mouth disease virus isolate O(1) Manisa in sheep milk samples. The majority of samples from animals vaccinated 14-23 weeks previously were indistinguishable from naive sheep when tested in the LPBE but 97% were positive using the SIA. All milk samples taken at 7 days after parturition from immunised animals were positive by LPBE. Thereafter, this proportion declined, although occasional reactors were detected at every stage up to 83 days. However, when mean titres were calculated for every sampling point after lambing, results were only positive for the first 18 days in this test. By contrast, the SIA was able to detect almost all (i.e. 97%) the vaccinated animals up to 83 days post parturition. Milk samples from convalescent animals all gave positive results in the assays. Sicilo-Sarde sheep gave higher titres on average than the Commisane breed at comparable stages after lambing. Both tests could be used for surveillance purposes following an outbreak of FMD to identify flocks of sheep which had been infected, but the SIA would be required to show the presence of vaccinated animals unless they were sampled soon after parturition.