In 1986, hemophiliacs treated with commercial concentrates of coagulation factors prepared from pools of plasma were at great risk to contract delta hepatitis infection. About 50 percent of these patients had delta hepatitis virus antibodies. Also, studies of small cohorts indicated that hepatitis delta infection was a major cause of chronic liver disease and cirrhosis. Therefore, there was a critical need to evaluate the frequency and effect of hepatitis delta infection in hemophiliacs, comparing those with presumed chronic non-A, non-B hepatitis, chronic hepatitis B alone, and combined chronic delta and HBV infections.