In the routine screening of blood donors, 30 asymptomatic donors were found to be positive for hepatitis-B antigen (HB Ag). They had no history suggestive of hepatitis in the past. None had antibody to HB Ag (HB Ab). Three were heroin addicts. All 30 donors were found to have demonstrable biochemical and histologic abnormalities of the liver. However, they have remained asymptomatic throughout the periods of HB antigenemia, which have ranged from 13 to 72 weeks. The immunoglobulins were normal in all of the donors. The cell-mediated immune response (CMIR), as tested by leukocyte migration inhibition, was normal in 16 subjects and was only slightly depressed in four, indicating that depression of CMIR is not the cause of this clinical state. Long-term observation of these individuals will be continued, with regular biochemical and histologic assessment to determine the natural course of this condition.