Evidence of past zoonotic infection was investigated serologically in randomly selected Northern Ireland farmers. The percentage of farmers with antibody was: Brucella abortus (0.7), Leptospira interrogans serovars (8.1), Borrelia burgdorferi (14.3), Toxoplasma gondii (73.5), Coxiella burnetii (28.0), Chlamydia psittaci (11.1) and Hantavirus (1.2). The results show that Northern Ireland farmers have been exposed in the past to zoonotic infections. It is not known if these infections contributed to ill health in farmers but it is now time for the health of farm workers and their medical services to be reassessed.