Four types of commercial antisera to citrus tristeza virus (CTV), two of which were monoclonal and two polyclonal, were compared in enzyme-linked immonosorbent assay (ELISA) tests against different CTV isolates from four Mediterranean countries: Italy, Turkey, Morocco and Cyprus. With the exception of one monoclonal antiserum, which failed to recognize a few virus isolates from Turkey and Cyprus, the four antisera were effective in CTV diagnosis which implies that the ELISA procedure can be employed for routine in certification programmes.