The incidence of occupationally acquired infectious diseases, has, up to now, been unknown. A reporting scheme for consultants in communicable disease control (CCDCs) (and their equivalents) throughout the United Kingdom was set up in October 1996 to estimate its extent. Monthly reporting cards were sent to CCDCs asking for brief details of all new cases of occupationally acquired infectious disease seen by them. Between October 1996 and September 1997, 1037 new cases were notified by CCDCs. The highest rates were among employees in food production and catering, farming, and among care workers, particularly in residential homes. During the same period an estimated 257 cases were reported in comparable surveillance schemes by chest physicians, occupational physicians and dermatologists. These figures probably underestimate the number of infections acquired in association with work substantially, and highlight diarrhoeal disease as the commonest problem.