Occult hepatitis B is HBsAg-negative hepatitis B, manifested by elevated serum transaminases or/and elevated bilirubin, with/without clinical symptoms, but the “two-and-a-half” test is “small two-positive”, “recovery three-positive”, “recovery two-positive” (please read: Understanding two-and-a-half, interpreting two-and-a-half). (Please read: Understanding the two and a half pairs, explaining the two and a half pairs). There is no reliable method to diagnose occult hepatitis B. The accepted and ideal, but impractical, diagnostic method is the detection of blood or/and liver hepatitis B virus nucleic acid or detection of hepatic hepatitis B virus antigen by more sensitive methods; however, a negative test still does not exclude occult hepatitis B because the virus nucleic acid or antigen manifests at low levels and does not reach detectable levels on a continuous basis, so many patients are missed. Clinical experience suggests that more patients with occult hepatitis B may be diagnosed than by currently accepted methods. An empirical diagnosis may take several years and usually requires the patient to be patient enough to cooperate with the physician’s ongoing observation and trial treatment. The most common confusion in clinical practice is that some patients with occult hepatitis B may also have positive autoantibodies, making it difficult for physicians to diagnose the patient as having hepatitis B or autoimmune hepatitis. Most patients with occult hepatitis B are unlikely to progress to cirrhosis, but some are already cirrhotic and tend to be decompensated; occult hepatitis B is less likely to progress to hepatocellular carcinoma than manifest hepatitis B, but is still a high risk for hepatocellular carcinoma. However, it is still a high-risk group for liver cancer. There have been some patients with occult hepatitis B who, after several years of trial treatment failure and switching to antiviral therapy, eventually achieved sustained remission or disappearance of liver disease-related symptoms and normalization or significant improvement in laboratory parameters, and who have continued for years with “small two-positive”, “recovered three-positive”, “recovered two-positive The positive conversion of “small two-positive”, “recovered three-positive”, and “recovered two-positive” (please read: Bi-directional evolution of two-and-a-half-pair performance pattern) also occurred.