Tuberculosis has been recognised as an important health problem among homeless persons. The New South Wales tuberculosis screening program for residents of hostels for the homeless has been in operation for several years, but has not yet been evaluated. This study reviewed the performance of the tuberculosis surveillance program (which uses mobile chest x-ray screening) between 1989 and 1993 at the five major hostels for homeless men in the eastern Sydney area. Reports of the screening x-rays and records of subsequent follow-up examinations at chest clinics were examined; information on cases detected by the screening program was compared with notifications in the same population. Of 3555 residents screened during 23 visits, 506 (14.2 per cent) were found to have an abnormal chest x-ray. However, only two active cases of tuberculosis were diagnosed as a result of the screening program, while seven cases were notified on the basis of clinical presentation. About 50 per cent of those with an abnormal chest x-ray from the screening program were lost to follow-up. Possible reasons for loss to follow-up were: long delays in making chest clinic appointments; short-stay residents changing shelters without trace; and high prevalence of severe mental illness or organic brain syndrome among residents. Raising awareness of the disease among primary health care and welfare staff who work with homeless men may be a more effective approach to improving identification of cases of active tuberculosis in this population.