Detailed screening of the patients and staff in a unit specializing in liver disease was carried out over a year to ascertain whether transmission of the serum hepatitis virus was occurring and whether the situation was comparable in any way to that found in a Renal Haemodialysis Unit. Of the 154 patients with liver disease tested on admission, 6% were found to have Australia antigen in the serum and throughout the year there were rarely less than two patients in the ward at any one time with positive serum. No instances of clinical hepatitis were detected in the other patients following their stay in the ward or in their attendant medical, nursing and lay staff. Six staff members were found to have Australia antigen in their serum. In four of these, all nurses, it was present in the first sample tested and so the infection may have been acquired earlier. Temporary elevations in both plasma bilirubin and serum aspartate aminotransferase levels were found in another five staff members whose serum was negative for Australia antigen and who clinically were well. In a further eight and apparently healthy staff members, an isolated but persistent elevation of the plasma bilirubin was noted. In both groups these changes could represent the spread of subclinical infectious hepatitis and it is recommended that in units dealing with ‘liver patients’ not only should considerable care be taken during diagnostic and therapeutic procedures but the medical and nursing staff should be screened at regular intervals.